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Foster 4 Series Couplers

The Foster 4 Series is the 3/8" body industrial interchange, one of the most common air coupler sizes for shop and industrial use. This collection includes 4 Series couplers and plugs in brass, steel, and stainless with NPT, hose barb, push-on, and reusable terminations. Filter by thread, material, and coupler or plug to match your line.

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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass Save 20% Save %
$ 630.00
$ 630.00 - $ 630.00
$ 630.00
$ 504.00
$ 504.00 - $ 504.00
$ 504.00

Foster SL4204, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL4204 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 630.00
$ 630.00 - $ 630.00
$ 630.00
$ 504.00
$ 504.00 - $ 504.00
$ 504.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass Save 20% Save %
$ 552.00
$ 552.00 - $ 552.00
$ 552.00
$ 442.00
$ 442.00 - $ 442.00
$ 442.00

Foster FM4204, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4204 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 552.00
$ 552.00 - $ 552.00
$ 552.00
$ 442.00
$ 442.00 - $ 442.00
$ 442.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass Save 20% Save %
$ 619.00
$ 619.00 - $ 619.00
$ 619.00
$ 495.00
$ 495.00 - $ 495.00
$ 495.00

Foster SL4004, 3/8" Industrial Coupler x 1/4" Female NPT, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL4004 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 619.00
$ 619.00 - $ 619.00
$ 619.00
$ 495.00
$ 495.00 - $ 495.00
$ 495.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass Save 20% Save %
$ 549.00
$ 549.00 - $ 549.00
$ 549.00
$ 438.00
$ 438.00 - $ 438.00
$ 438.00

Foster FM4004, 3/8" Industrial Coupler x 1/4" Female NPT, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4004 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 549.00
$ 549.00 - $ 549.00
$ 549.00
$ 438.00
$ 438.00 - $ 438.00
$ 438.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 557.00
$ 557.00 - $ 557.00
$ 557.00
$ 445.00
$ 445.00 - $ 445.00
$ 445.00

Foster SD13-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 13/16" OD, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SD13-4 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 557.00
$ 557.00 - $ 557.00
$ 557.00
$ 445.00
$ 445.00 - $ 445.00
$ 445.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 537.00
$ 537.00 - $ 537.00
$ 537.00
$ 430.00
$ 430.00 - $ 430.00
$ 430.00

Foster SD11-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 3/4" OD, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SD11-4 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 537.00
$ 537.00 - $ 537.00
$ 537.00
$ 430.00
$ 430.00 - $ 430.00
$ 430.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 624.00
$ 624.00 - $ 624.00
$ 624.00
$ 500.00
$ 500.00 - $ 500.00
$ 500.00

Foster BLSD9-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 11/16" OD, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BLSD9-4 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series ...

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$ 624.00
$ 624.00 - $ 624.00
$ 624.00
$ 500.00
$ 500.00 - $ 500.00
$ 500.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 523.00
$ 523.00 - $ 523.00
$ 523.00
$ 419.00
$ 419.00 - $ 419.00
$ 419.00

Foster SD9-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 11/16" OD, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SD9-4 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — ...

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$ 523.00
$ 523.00 - $ 523.00
$ 523.00
$ 419.00
$ 419.00 - $ 419.00
$ 419.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 614.00
$ 614.00 - $ 614.00
$ 614.00
$ 492.00
$ 492.00 - $ 492.00
$ 492.00

Foster BLSD7-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 5/8" OD, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BLSD7-4 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series ...

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$ 614.00
$ 614.00 - $ 614.00
$ 614.00
$ 492.00
$ 492.00 - $ 492.00
$ 492.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 514.00
$ 514.00 - $ 514.00
$ 514.00
$ 411.00
$ 411.00 - $ 411.00
$ 411.00

Foster SD7-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 5/8" OD, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SD7-4 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — ...

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$ 514.00
$ 514.00 - $ 514.00
$ 514.00
$ 411.00
$ 411.00 - $ 411.00
$ 411.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 600.00
$ 600.00 - $ 600.00
$ 600.00
$ 480.00
$ 480.00 - $ 480.00
$ 480.00

Foster SB7-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 1/4" ID x 5/8" OD, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SB7-4 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — ...

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$ 600.00
$ 600.00 - $ 600.00
$ 600.00
$ 480.00
$ 480.00 - $ 480.00
$ 480.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 612.00
$ 612.00 - $ 612.00
$ 612.00
$ 490.00
$ 490.00 - $ 490.00
$ 490.00

Foster SB5-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 1/4" ID x 9/16" OD, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SB5-4 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — ...

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$ 612.00
$ 612.00 - $ 612.00
$ 612.00
$ 490.00
$ 490.00 - $ 490.00
$ 490.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 583.00
$ 583.00 - $ 583.00
$ 583.00
$ 468.00
$ 468.00 - $ 468.00
$ 468.00

Foster SB3-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 1/4" ID x 1/2" OD, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SB3-4 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — ...

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$ 583.00
$ 583.00 - $ 583.00
$ 583.00
$ 468.00
$ 468.00 - $ 468.00
$ 468.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 595.00
$ 595.00 - $ 595.00
$ 595.00
$ 476.00
$ 476.00 - $ 476.00
$ 476.00

Foster 1814W, 3/8" Industrial Coupler x 1/2" Push-On Hose Stem, 4 Series, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 1814W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 595.00
$ 595.00 - $ 595.00
$ 595.00
$ 476.00
$ 476.00 - $ 476.00
$ 476.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 500.00
$ 500.00 - $ 500.00
$ 500.00
$ 400.00
$ 400.00 - $ 400.00
$ 400.00

Foster BL1814, 3/8" Industrial Coupler x 1/2" Push-On Hose Stem, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL1814 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 500.00
$ 500.00 - $ 500.00
$ 500.00
$ 400.00
$ 400.00 - $ 400.00
$ 400.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
Save 20% Save %
$ 474.00
$ 474.00 - $ 474.00
$ 474.00
$ 380.00
$ 380.00 - $ 380.00
$ 380.00

Foster 1814, 3/8" Industrial Coupler x 1/2" Push-On Hose Stem, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 1814 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 474.00
$ 474.00 - $ 474.00
$ 474.00
$ 380.00
$ 380.00 - $ 380.00
$ 380.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 564.00
$ 564.00 - $ 564.00
$ 564.00
$ 450.00
$ 450.00 - $ 450.00
$ 450.00

Foster 1714W, 3/8" Industrial Coupler x 3/8" Push-On Hose Stem, 4 Series, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 1714W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 564.00
$ 564.00 - $ 564.00
$ 564.00
$ 450.00
$ 450.00 - $ 450.00
$ 450.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
Save 20% Save %
$ 468.00
$ 468.00 - $ 468.00
$ 468.00
$ 374.00
$ 374.00 - $ 374.00
$ 374.00

Foster BL1714, 3/8" Industrial Coupler x 3/8" Push-On Hose Stem, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL1714 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 468.00
$ 468.00 - $ 468.00
$ 468.00
$ 374.00
$ 374.00 - $ 374.00
$ 374.00
Save 20% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
Save 20% Save %
$ 431.00
$ 431.00 - $ 431.00
$ 431.00
$ 345.00
$ 345.00 - $ 345.00
$ 345.00

Foster 1714, 3/8" Industrial Coupler x 3/8" Push-On Hose Stem, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 1714 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 431.00
$ 431.00 - $ 431.00
$ 431.00
$ 345.00
$ 345.00 - $ 345.00
$ 345.00
Save 20% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 576.00
$ 576.00 - $ 576.00
$ 576.00
$ 462.00
$ 462.00 - $ 462.00
$ 462.00

Foster 4904S, 3/8" Industrial Coupler x 1/2" Hose ID, 4 Series, Steam/EPDM, Brass body, Brass sleeve, SS valve

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4904S is a Brass body, Brass sleeve, SS valve 3/8" industrial coupler from...

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$ 576.00
$ 576.00 - $ 576.00
$ 576.00
$ 462.00
$ 462.00 - $ 462.00
$ 462.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 587.00
$ 587.00 - $ 587.00
$ 587.00
$ 469.00
$ 469.00 - $ 469.00
$ 469.00

Foster BL4904, 3/8" Industrial Coupler x 1/2" Hose ID, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4904 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 587.00
$ 587.00 - $ 587.00
$ 587.00
$ 469.00
$ 469.00 - $ 469.00
$ 469.00
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
Save 20% Save %
$ 473.00
$ 473.00 - $ 473.00
$ 473.00
$ 378.00
$ 378.00 - $ 378.00
$ 378.00

Foster 4904, 3/8" Industrial Coupler x 1/2" Hose ID, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4904 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 473.00
$ 473.00 - $ 473.00
$ 473.00
$ 378.00
$ 378.00 - $ 378.00
$ 378.00
Save 20% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
Save 20% Save %
$ 559.00
$ 559.00 - $ 559.00
$ 559.00
$ 447.00
$ 447.00 - $ 447.00
$ 447.00

Foster 4804W, 3/8" Industrial Coupler x 3/8" Hose ID, 4 Series, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4804W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 559.00
$ 559.00 - $ 559.00
$ 559.00
$ 447.00
$ 447.00 - $ 447.00
$ 447.00
Save 20% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 595.00
$ 595.00 - $ 595.00
$ 595.00
$ 476.00
$ 476.00 - $ 476.00
$ 476.00

Foster 4804S, 3/8" Industrial Coupler x 3/8" Hose ID, 4 Series, Steam/EPDM, Brass body, Brass sleeve, SS valve

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4804S is a Brass body, Brass sleeve, SS valve 3/8" industrial coupler from...

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$ 595.00
$ 595.00 - $ 595.00
$ 595.00
$ 476.00
$ 476.00 - $ 476.00
$ 476.00
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