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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 %
$ 863.00
$ 863.00 - $ 863.00
$ 863.00
$ 689.00
$ 689.00 - $ 689.00
$ 689.00

Foster 4804S/S, 3/8" Industrial Coupler x 3/8" Hose ID, 4 Series, 303 Stainless

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4804S/S is a 303 Stainless 3/8" industrial coupler from the Foster 4 Serie...

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$ 863.00
$ 863.00 - $ 863.00
$ 863.00
$ 689.00
$ 689.00 - $ 689.00
$ 689.00
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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 %
$ 579.00
$ 579.00 - $ 579.00
$ 579.00
$ 464.00
$ 464.00 - $ 464.00
$ 464.00

Foster BL4804, 3/8" Industrial Coupler x 3/8" Hose ID, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4804 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
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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 %
$ 486.00
$ 486.00 - $ 486.00
$ 486.00
$ 390.00
$ 390.00 - $ 390.00
$ 390.00

Foster 4804, 3/8" Industrial Coupler x 3/8" Hose ID, 4 Series, Brass/Steel

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

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$ 486.00
$ 486.00 - $ 486.00
$ 486.00
$ 390.00
$ 390.00 - $ 390.00
$ 390.00
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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 %
$ 569.00
$ 569.00 - $ 569.00
$ 569.00
$ 455.00
$ 455.00 - $ 455.00
$ 455.00

Foster BL4704, 3/8" Industrial Coupler x 5/16" Hose ID, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4704 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
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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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$ 496.00
$ 496.00 - $ 496.00
$ 496.00
$ 396.00
$ 396.00 - $ 396.00
$ 396.00

Foster 4704, 3/8" Industrial Coupler x 5/16" Hose ID, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4704 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 496.00
$ 496.00 - $ 496.00
$ 496.00
$ 396.00
$ 396.00 - $ 396.00
$ 396.00
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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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$ 558.00
$ 558.00 - $ 558.00
$ 558.00
$ 448.00
$ 448.00 - $ 448.00
$ 448.00

Foster 4604W, 3/8" Industrial Coupler x 1/4" Hose ID, 4 Series, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4604W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 558.00
$ 558.00 - $ 558.00
$ 558.00
$ 448.00
$ 448.00 - $ 448.00
$ 448.00
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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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$ 562.00
$ 562.00 - $ 562.00
$ 562.00
$ 450.00
$ 450.00 - $ 450.00
$ 450.00

Foster BL4604, 3/8" Industrial Coupler x 1/4" Hose ID, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4604 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 562.00
$ 562.00 - $ 562.00
$ 562.00
$ 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
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$ 472.00
$ 472.00 - $ 472.00
$ 472.00
$ 377.00
$ 377.00 - $ 377.00
$ 377.00

Foster 4604, 3/8" Industrial Coupler x 1/4" Hose ID, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4604 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 472.00
$ 472.00 - $ 472.00
$ 472.00
$ 377.00
$ 377.00 - $ 377.00
$ 377.00
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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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$ 576.00
$ 576.00 - $ 576.00
$ 576.00
$ 462.00
$ 462.00 - $ 462.00
$ 462.00

Foster 4504W, 3/8" Industrial Coupler x 1/2" Male NPT, 4 Series, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4504W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 576.00
$ 576.00 - $ 576.00
$ 576.00
$ 462.00
$ 462.00 - $ 462.00
$ 462.00
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 %
$ 569.00
$ 569.00 - $ 569.00
$ 569.00
$ 455.00
$ 455.00 - $ 455.00
$ 455.00

Foster 4504S, 3/8" Industrial Coupler x 1/2" Male NPT, 4 Series, Steam/EPDM, Brass body, Brass sleeve, SS valve

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4504S is a Brass body, Brass sleeve, SS valve 3/8" industrial coupler from...

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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
Save 20% Save %
$ 569.00
$ 569.00 - $ 569.00
$ 569.00
$ 455.00
$ 455.00 - $ 455.00
$ 455.00

Foster 4504H, 3/8" Industrial Coupler x 1/2" Male NPT, 4 Series, Heat/Viton, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4504H 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
Save 20% Save %
$ 572.00
$ 572.00 - $ 572.00
$ 572.00
$ 458.00
$ 458.00 - $ 458.00
$ 458.00

Foster BL4504, 3/8" Industrial Coupler x 1/2" Male NPT, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4504 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 572.00
$ 572.00 - $ 572.00
$ 572.00
$ 458.00
$ 458.00 - $ 458.00
$ 458.00
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 %
$ 483.00
$ 483.00 - $ 483.00
$ 483.00
$ 386.00
$ 386.00 - $ 386.00
$ 386.00

Foster 4504, 3/8" Industrial Coupler x 1/2" Male NPT, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4504 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 483.00
$ 483.00 - $ 483.00
$ 483.00
$ 386.00
$ 386.00 - $ 386.00
$ 386.00
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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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$ 508.00
$ 508.00 - $ 508.00
$ 508.00
$ 407.00
$ 407.00 - $ 407.00
$ 407.00

Foster 4304W, 3/8" Industrial Coupler x 3/8" Male NPT, 4 Series, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4304W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 508.00
$ 508.00 - $ 508.00
$ 508.00
$ 407.00
$ 407.00 - $ 407.00
$ 407.00
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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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$ 867.00
$ 867.00 - $ 867.00
$ 867.00
$ 693.00
$ 693.00 - $ 693.00
$ 693.00

Foster BL4304S/S, 3/8" Industrial Coupler x 3/8" Male NPT, 4 Series, Ball Lock, 303 Stainless

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4304S/S is a 303 Stainless 3/8" industrial coupler from the Foster 4 Ser...

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$ 867.00
$ 867.00 - $ 867.00
$ 867.00
$ 693.00
$ 693.00 - $ 693.00
$ 693.00
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 %
$ 851.00
$ 851.00 - $ 851.00
$ 851.00
$ 681.00
$ 681.00 - $ 681.00
$ 681.00

Foster 4304S/S, 3/8" Industrial Coupler x 3/8" Male NPT, 4 Series, 303 Stainless

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4304S/S is a 303 Stainless 3/8" industrial coupler from the Foster 4 Serie...

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$ 851.00
$ 851.00 - $ 851.00
$ 851.00
$ 681.00
$ 681.00 - $ 681.00
$ 681.00
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 %
$ 520.00
$ 520.00 - $ 520.00
$ 520.00
$ 415.00
$ 415.00 - $ 415.00
$ 415.00

Foster 4304S, 3/8" Industrial Coupler x 3/8" Male NPT, 4 Series, Steam/EPDM, Brass body, Brass sleeve, SS valve

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4304S is a Brass body, Brass sleeve, SS valve 3/8" industrial coupler from...

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$ 520.00
$ 520.00 - $ 520.00
$ 520.00
$ 415.00
$ 415.00 - $ 415.00
$ 415.00
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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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$ 505.00
$ 505.00 - $ 505.00
$ 505.00
$ 405.00
$ 405.00 - $ 405.00
$ 405.00

Foster BL4304, 3/8" Industrial Coupler x 3/8" Male NPT, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4304 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 505.00
$ 505.00 - $ 505.00
$ 505.00
$ 405.00
$ 405.00 - $ 405.00
$ 405.00
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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$ 434.00
$ 434.00 - $ 434.00
$ 434.00
$ 346.00
$ 346.00 - $ 346.00
$ 346.00

Foster 4304, 3/8" Industrial Coupler x 3/8" Male NPT, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4304 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 434.00
$ 434.00 - $ 434.00
$ 434.00
$ 346.00
$ 346.00 - $ 346.00
$ 346.00
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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$ 488.00
$ 488.00 - $ 488.00
$ 488.00
$ 391.00
$ 391.00 - $ 391.00
$ 391.00

Foster 4104W, 3/8" Industrial Coupler x 1/4" Male NPT, 4 Series, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4104W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 488.00
$ 488.00 - $ 488.00
$ 488.00
$ 391.00
$ 391.00 - $ 391.00
$ 391.00
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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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$ 501.00
$ 501.00 - $ 501.00
$ 501.00
$ 402.00
$ 402.00 - $ 402.00
$ 402.00

Foster 4104S, 3/8" Industrial Coupler x 1/4" Male NPT, 4 Series, Steam/EPDM, Brass body, Brass sleeve, SS valve

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4104S is a Brass body, Brass sleeve, SS valve 3/8" industrial coupler from...

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$ 501.00
$ 501.00 - $ 501.00
$ 501.00
$ 402.00
$ 402.00 - $ 402.00
$ 402.00
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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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$ 481.00
$ 481.00 - $ 481.00
$ 481.00
$ 384.00
$ 384.00 - $ 384.00
$ 384.00

Foster 4104H, 3/8" Industrial Coupler x 1/4" Male NPT, 4 Series, Heat/Viton, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4104H is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — ...

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$ 481.00
$ 481.00 - $ 481.00
$ 481.00
$ 384.00
$ 384.00 - $ 384.00
$ 384.00
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 %
$ 484.00
$ 484.00 - $ 484.00
$ 484.00
$ 388.00
$ 388.00 - $ 388.00
$ 388.00

Foster BL4104, 3/8" Industrial Coupler x 1/4" Male NPT, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4104 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 484.00
$ 484.00 - $ 484.00
$ 484.00
$ 388.00
$ 388.00 - $ 388.00
$ 388.00
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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$ 415.00
$ 415.00 - $ 415.00
$ 415.00
$ 333.00
$ 333.00 - $ 333.00
$ 333.00

Foster 4104, 3/8" Industrial Coupler x 1/4" Male NPT, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4104 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 415.00
$ 415.00 - $ 415.00
$ 415.00
$ 333.00
$ 333.00 - $ 333.00
$ 333.00
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