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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 %
$ 697.00
$ 697.00 - $ 697.00
$ 697.00
$ 558.00
$ 558.00 - $ 558.00
$ 558.00

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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$ 697.00
$ 697.00 - $ 697.00
$ 697.00
$ 558.00
$ 558.00 - $ 558.00
$ 558.00
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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 %
$ 611.00
$ 611.00 - $ 611.00
$ 611.00
$ 489.00
$ 489.00 - $ 489.00
$ 489.00

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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$ 611.00
$ 611.00 - $ 611.00
$ 611.00
$ 489.00
$ 489.00 - $ 489.00
$ 489.00
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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 %
$ 686.00
$ 686.00 - $ 686.00
$ 686.00
$ 548.00
$ 548.00 - $ 548.00
$ 548.00

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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$ 686.00
$ 686.00 - $ 686.00
$ 686.00
$ 548.00
$ 548.00 - $ 548.00
$ 548.00
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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 %
$ 607.00
$ 607.00 - $ 607.00
$ 607.00
$ 485.00
$ 485.00 - $ 485.00
$ 485.00

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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$ 607.00
$ 607.00 - $ 607.00
$ 607.00
$ 485.00
$ 485.00 - $ 485.00
$ 485.00
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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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$ 617.00
$ 617.00 - $ 617.00
$ 617.00
$ 493.00
$ 493.00 - $ 493.00
$ 493.00

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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$ 617.00
$ 617.00 - $ 617.00
$ 617.00
$ 493.00
$ 493.00 - $ 493.00
$ 493.00
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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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$ 594.00
$ 594.00 - $ 594.00
$ 594.00
$ 476.00
$ 476.00 - $ 476.00
$ 476.00

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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$ 594.00
$ 594.00 - $ 594.00
$ 594.00
$ 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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$ 691.00
$ 691.00 - $ 691.00
$ 691.00
$ 554.00
$ 554.00 - $ 554.00
$ 554.00

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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$ 691.00
$ 691.00 - $ 691.00
$ 691.00
$ 554.00
$ 554.00 - $ 554.00
$ 554.00
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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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$ 579.00
$ 579.00 - $ 579.00
$ 579.00
$ 464.00
$ 464.00 - $ 464.00
$ 464.00

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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$ 579.00
$ 579.00 - $ 579.00
$ 579.00
$ 464.00
$ 464.00 - $ 464.00
$ 464.00
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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$ 680.00
$ 680.00 - $ 680.00
$ 680.00
$ 544.00
$ 544.00 - $ 544.00
$ 544.00

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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$ 680.00
$ 680.00 - $ 680.00
$ 680.00
$ 544.00
$ 544.00 - $ 544.00
$ 544.00
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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$ 569.00
$ 569.00 - $ 569.00
$ 569.00
$ 455.00
$ 455.00 - $ 455.00
$ 455.00

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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$ 569.00
$ 569.00 - $ 569.00
$ 569.00
$ 455.00
$ 455.00 - $ 455.00
$ 455.00
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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$ 665.00
$ 665.00 - $ 665.00
$ 665.00
$ 531.00
$ 531.00 - $ 531.00
$ 531.00

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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$ 665.00
$ 665.00 - $ 665.00
$ 665.00
$ 531.00
$ 531.00 - $ 531.00
$ 531.00
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 %
$ 678.00
$ 678.00 - $ 678.00
$ 678.00
$ 542.00
$ 542.00 - $ 542.00
$ 542.00

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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$ 678.00
$ 678.00 - $ 678.00
$ 678.00
$ 542.00
$ 542.00 - $ 542.00
$ 542.00
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 %
$ 646.00
$ 646.00 - $ 646.00
$ 646.00
$ 518.00
$ 518.00 - $ 518.00
$ 518.00

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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$ 646.00
$ 646.00 - $ 646.00
$ 646.00
$ 518.00
$ 518.00 - $ 518.00
$ 518.00
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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$ 659.00
$ 659.00 - $ 659.00
$ 659.00
$ 527.00
$ 527.00 - $ 527.00
$ 527.00

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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$ 659.00
$ 659.00 - $ 659.00
$ 659.00
$ 527.00
$ 527.00 - $ 527.00
$ 527.00
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 %
$ 554.00
$ 554.00 - $ 554.00
$ 554.00
$ 443.00
$ 443.00 - $ 443.00
$ 443.00

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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$ 554.00
$ 554.00 - $ 554.00
$ 554.00
$ 443.00
$ 443.00 - $ 443.00
$ 443.00
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 %
$ 525.00
$ 525.00 - $ 525.00
$ 525.00
$ 420.00
$ 420.00 - $ 420.00
$ 420.00

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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$ 525.00
$ 525.00 - $ 525.00
$ 525.00
$ 420.00
$ 420.00 - $ 420.00
$ 420.00
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 %
$ 625.00
$ 625.00 - $ 625.00
$ 625.00
$ 499.00
$ 499.00 - $ 499.00
$ 499.00

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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$ 625.00
$ 625.00 - $ 625.00
$ 625.00
$ 499.00
$ 499.00 - $ 499.00
$ 499.00
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 %
$ 518.00
$ 518.00 - $ 518.00
$ 518.00
$ 415.00
$ 415.00 - $ 415.00
$ 415.00

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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$ 518.00
$ 518.00 - $ 518.00
$ 518.00
$ 415.00
$ 415.00 - $ 415.00
$ 415.00
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 %
$ 478.00
$ 478.00 - $ 478.00
$ 478.00
$ 382.00
$ 382.00 - $ 382.00
$ 382.00

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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$ 478.00
$ 478.00 - $ 478.00
$ 478.00
$ 382.00
$ 382.00 - $ 382.00
$ 382.00
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 %
$ 638.00
$ 638.00 - $ 638.00
$ 638.00
$ 512.00
$ 512.00 - $ 512.00
$ 512.00

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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$ 638.00
$ 638.00 - $ 638.00
$ 638.00
$ 512.00
$ 512.00 - $ 512.00
$ 512.00
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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$ 649.00
$ 649.00 - $ 649.00
$ 649.00
$ 520.00
$ 520.00 - $ 520.00
$ 520.00

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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$ 649.00
$ 649.00 - $ 649.00
$ 649.00
$ 520.00
$ 520.00 - $ 520.00
$ 520.00
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 %
$ 523.00
$ 523.00 - $ 523.00
$ 523.00
$ 418.00
$ 418.00 - $ 418.00
$ 418.00

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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$ 523.00
$ 523.00 - $ 523.00
$ 523.00
$ 418.00
$ 418.00 - $ 418.00
$ 418.00
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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$ 619.00
$ 619.00 - $ 619.00
$ 619.00
$ 495.00
$ 495.00 - $ 495.00
$ 495.00

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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$ 619.00
$ 619.00 - $ 619.00
$ 619.00
$ 495.00
$ 495.00 - $ 495.00
$ 495.00
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 %
$ 659.00
$ 659.00 - $ 659.00
$ 659.00
$ 527.00
$ 527.00 - $ 527.00
$ 527.00

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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$ 659.00
$ 659.00 - $ 659.00
$ 659.00
$ 527.00
$ 527.00 - $ 527.00
$ 527.00
Save 20% Save %

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