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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 %
$ 952.00
$ 952.00 - $ 952.00
$ 952.00
$ 760.00
$ 760.00 - $ 760.00
$ 760.00

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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$ 952.00
$ 952.00 - $ 952.00
$ 952.00
$ 760.00
$ 760.00 - $ 760.00
$ 760.00
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 %
$ 639.00
$ 639.00 - $ 639.00
$ 639.00
$ 512.00
$ 512.00 - $ 512.00
$ 512.00

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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$ 639.00
$ 639.00 - $ 639.00
$ 639.00
$ 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 Save 20% Save %
$ 536.00
$ 536.00 - $ 536.00
$ 536.00
$ 430.00
$ 430.00 - $ 430.00
$ 430.00

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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$ 536.00
$ 536.00 - $ 536.00
$ 536.00
$ 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 Save 20% Save %
$ 627.00
$ 627.00 - $ 627.00
$ 627.00
$ 502.00
$ 502.00 - $ 502.00
$ 502.00

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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$ 627.00
$ 627.00 - $ 627.00
$ 627.00
$ 502.00
$ 502.00 - $ 502.00
$ 502.00
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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 %
$ 548.00
$ 548.00 - $ 548.00
$ 548.00
$ 437.00
$ 437.00 - $ 437.00
$ 437.00

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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$ 548.00
$ 548.00 - $ 548.00
$ 548.00
$ 437.00
$ 437.00 - $ 437.00
$ 437.00
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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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$ 616.00
$ 616.00 - $ 616.00
$ 616.00
$ 494.00
$ 494.00 - $ 494.00
$ 494.00

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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$ 616.00
$ 616.00 - $ 616.00
$ 616.00
$ 494.00
$ 494.00 - $ 494.00
$ 494.00
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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 %
$ 620.00
$ 620.00 - $ 620.00
$ 620.00
$ 496.00
$ 496.00 - $ 496.00
$ 496.00

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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$ 620.00
$ 620.00 - $ 620.00
$ 620.00
$ 496.00
$ 496.00 - $ 496.00
$ 496.00
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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 %
$ 521.00
$ 521.00 - $ 521.00
$ 521.00
$ 416.00
$ 416.00 - $ 416.00
$ 416.00

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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$ 521.00
$ 521.00 - $ 521.00
$ 521.00
$ 416.00
$ 416.00 - $ 416.00
$ 416.00
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 %
$ 635.00
$ 635.00 - $ 635.00
$ 635.00
$ 510.00
$ 510.00 - $ 510.00
$ 510.00

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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$ 635.00
$ 635.00 - $ 635.00
$ 635.00
$ 510.00
$ 510.00 - $ 510.00
$ 510.00
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 %
$ 627.00
$ 627.00 - $ 627.00
$ 627.00
$ 502.00
$ 502.00 - $ 502.00
$ 502.00

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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$ 627.00
$ 627.00 - $ 627.00
$ 627.00
$ 502.00
$ 502.00 - $ 502.00
$ 502.00
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 %
$ 627.00
$ 627.00 - $ 627.00
$ 627.00
$ 502.00
$ 502.00 - $ 502.00
$ 502.00

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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$ 627.00
$ 627.00 - $ 627.00
$ 627.00
$ 502.00
$ 502.00 - $ 502.00
$ 502.00
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 %
$ 631.00
$ 631.00 - $ 631.00
$ 631.00
$ 506.00
$ 506.00 - $ 506.00
$ 506.00

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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$ 631.00
$ 631.00 - $ 631.00
$ 631.00
$ 506.00
$ 506.00 - $ 506.00
$ 506.00
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 %
$ 532.00
$ 532.00 - $ 532.00
$ 532.00
$ 426.00
$ 426.00 - $ 426.00
$ 426.00

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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$ 532.00
$ 532.00 - $ 532.00
$ 532.00
$ 426.00
$ 426.00 - $ 426.00
$ 426.00
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 %
$ 561.00
$ 561.00 - $ 561.00
$ 561.00
$ 449.00
$ 449.00 - $ 449.00
$ 449.00

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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$ 561.00
$ 561.00 - $ 561.00
$ 561.00
$ 449.00
$ 449.00 - $ 449.00
$ 449.00
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 %
$ 956.00
$ 956.00 - $ 956.00
$ 956.00
$ 764.00
$ 764.00 - $ 764.00
$ 764.00

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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$ 956.00
$ 956.00 - $ 956.00
$ 956.00
$ 764.00
$ 764.00 - $ 764.00
$ 764.00
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 %
$ 939.00
$ 939.00 - $ 939.00
$ 939.00
$ 751.00
$ 751.00 - $ 751.00
$ 751.00

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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$ 939.00
$ 939.00 - $ 939.00
$ 939.00
$ 751.00
$ 751.00 - $ 751.00
$ 751.00
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 %
$ 574.00
$ 574.00 - $ 574.00
$ 574.00
$ 458.00
$ 458.00 - $ 458.00
$ 458.00

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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$ 574.00
$ 574.00 - $ 574.00
$ 574.00
$ 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 %
$ 557.00
$ 557.00 - $ 557.00
$ 557.00
$ 447.00
$ 447.00 - $ 447.00
$ 447.00

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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$ 557.00
$ 557.00 - $ 557.00
$ 557.00
$ 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
Save 20% Save %
$ 479.00
$ 479.00 - $ 479.00
$ 479.00
$ 382.00
$ 382.00 - $ 382.00
$ 382.00

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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$ 479.00
$ 479.00 - $ 479.00
$ 479.00
$ 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 %
$ 538.00
$ 538.00 - $ 538.00
$ 538.00
$ 432.00
$ 432.00 - $ 432.00
$ 432.00

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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$ 538.00
$ 538.00 - $ 538.00
$ 538.00
$ 432.00
$ 432.00 - $ 432.00
$ 432.00
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 %
$ 553.00
$ 553.00 - $ 553.00
$ 553.00
$ 443.00
$ 443.00 - $ 443.00
$ 443.00

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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$ 553.00
$ 553.00 - $ 553.00
$ 553.00
$ 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 %
$ 531.00
$ 531.00 - $ 531.00
$ 531.00
$ 424.00
$ 424.00 - $ 424.00
$ 424.00

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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$ 531.00
$ 531.00 - $ 531.00
$ 531.00
$ 424.00
$ 424.00 - $ 424.00
$ 424.00
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 %
$ 534.00
$ 534.00 - $ 534.00
$ 534.00
$ 428.00
$ 428.00 - $ 428.00
$ 428.00

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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$ 534.00
$ 534.00 - $ 534.00
$ 534.00
$ 428.00
$ 428.00 - $ 428.00
$ 428.00
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 %
$ 458.00
$ 458.00 - $ 458.00
$ 458.00
$ 367.00
$ 367.00 - $ 367.00
$ 367.00

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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$ 458.00
$ 458.00 - $ 458.00
$ 458.00
$ 367.00
$ 367.00 - $ 367.00
$ 367.00
Save 20% Save %

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