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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 %
$ 887.00
$ 887.00 - $ 887.00
$ 887.00
$ 708.00
$ 708.00 - $ 708.00
$ 708.00

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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$ 887.00
$ 887.00 - $ 887.00
$ 887.00
$ 708.00
$ 708.00 - $ 708.00
$ 708.00
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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 %
$ 595.00
$ 595.00 - $ 595.00
$ 595.00
$ 476.00
$ 476.00 - $ 476.00
$ 476.00

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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$ 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 Save 20% Save %
$ 499.00
$ 499.00 - $ 499.00
$ 499.00
$ 400.00
$ 400.00 - $ 400.00
$ 400.00

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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$ 499.00
$ 499.00 - $ 499.00
$ 499.00
$ 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 %
$ 584.00
$ 584.00 - $ 584.00
$ 584.00
$ 468.00
$ 468.00 - $ 468.00
$ 468.00

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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$ 584.00
$ 584.00 - $ 584.00
$ 584.00
$ 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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$ 510.00
$ 510.00 - $ 510.00
$ 510.00
$ 407.00
$ 407.00 - $ 407.00
$ 407.00

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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$ 510.00
$ 510.00 - $ 510.00
$ 510.00
$ 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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$ 574.00
$ 574.00 - $ 574.00
$ 574.00
$ 461.00
$ 461.00 - $ 461.00
$ 461.00

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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$ 574.00
$ 574.00 - $ 574.00
$ 574.00
$ 461.00
$ 461.00 - $ 461.00
$ 461.00
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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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$ 577.00
$ 577.00 - $ 577.00
$ 577.00
$ 462.00
$ 462.00 - $ 462.00
$ 462.00

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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$ 577.00
$ 577.00 - $ 577.00
$ 577.00
$ 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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$ 485.00
$ 485.00 - $ 485.00
$ 485.00
$ 388.00
$ 388.00 - $ 388.00
$ 388.00

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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$ 485.00
$ 485.00 - $ 485.00
$ 485.00
$ 388.00
$ 388.00 - $ 388.00
$ 388.00
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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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$ 591.00
$ 591.00 - $ 591.00
$ 591.00
$ 475.00
$ 475.00 - $ 475.00
$ 475.00

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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$ 591.00
$ 591.00 - $ 591.00
$ 591.00
$ 475.00
$ 475.00 - $ 475.00
$ 475.00
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 %
$ 584.00
$ 584.00 - $ 584.00
$ 584.00
$ 468.00
$ 468.00 - $ 468.00
$ 468.00

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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$ 584.00
$ 584.00 - $ 584.00
$ 584.00
$ 468.00
$ 468.00 - $ 468.00
$ 468.00
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 %
$ 584.00
$ 584.00 - $ 584.00
$ 584.00
$ 468.00
$ 468.00 - $ 468.00
$ 468.00

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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$ 584.00
$ 584.00 - $ 584.00
$ 584.00
$ 468.00
$ 468.00 - $ 468.00
$ 468.00
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 %
$ 588.00
$ 588.00 - $ 588.00
$ 588.00
$ 471.00
$ 471.00 - $ 471.00
$ 471.00

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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$ 588.00
$ 588.00 - $ 588.00
$ 588.00
$ 471.00
$ 471.00 - $ 471.00
$ 471.00
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 %
$ 496.00
$ 496.00 - $ 496.00
$ 496.00
$ 397.00
$ 397.00 - $ 397.00
$ 397.00

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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$ 496.00
$ 496.00 - $ 496.00
$ 496.00
$ 397.00
$ 397.00 - $ 397.00
$ 397.00
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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 %
$ 522.00
$ 522.00 - $ 522.00
$ 522.00
$ 418.00
$ 418.00 - $ 418.00
$ 418.00

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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$ 522.00
$ 522.00 - $ 522.00
$ 522.00
$ 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
Save 20% Save %
$ 891.00
$ 891.00 - $ 891.00
$ 891.00
$ 712.00
$ 712.00 - $ 712.00
$ 712.00

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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$ 891.00
$ 891.00 - $ 891.00
$ 891.00
$ 712.00
$ 712.00 - $ 712.00
$ 712.00
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 %
$ 875.00
$ 875.00 - $ 875.00
$ 875.00
$ 699.00
$ 699.00 - $ 699.00
$ 699.00

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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$ 875.00
$ 875.00 - $ 875.00
$ 875.00
$ 699.00
$ 699.00 - $ 699.00
$ 699.00
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 %
$ 535.00
$ 535.00 - $ 535.00
$ 535.00
$ 427.00
$ 427.00 - $ 427.00
$ 427.00

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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$ 535.00
$ 535.00 - $ 535.00
$ 535.00
$ 427.00
$ 427.00 - $ 427.00
$ 427.00
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 %
$ 519.00
$ 519.00 - $ 519.00
$ 519.00
$ 416.00
$ 416.00 - $ 416.00
$ 416.00

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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$ 519.00
$ 519.00 - $ 519.00
$ 519.00
$ 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 %
$ 446.00
$ 446.00 - $ 446.00
$ 446.00
$ 356.00
$ 356.00 - $ 356.00
$ 356.00

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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$ 446.00
$ 446.00 - $ 446.00
$ 446.00
$ 356.00
$ 356.00 - $ 356.00
$ 356.00
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 %
$ 501.00
$ 501.00 - $ 501.00
$ 501.00
$ 402.00
$ 402.00 - $ 402.00
$ 402.00

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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$ 501.00
$ 501.00 - $ 501.00
$ 501.00
$ 402.00
$ 402.00 - $ 402.00
$ 402.00
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 %
$ 515.00
$ 515.00 - $ 515.00
$ 515.00
$ 413.00
$ 413.00 - $ 413.00
$ 413.00

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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$ 515.00
$ 515.00 - $ 515.00
$ 515.00
$ 413.00
$ 413.00 - $ 413.00
$ 413.00
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 %
$ 494.00
$ 494.00 - $ 494.00
$ 494.00
$ 395.00
$ 395.00 - $ 395.00
$ 395.00

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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$ 494.00
$ 494.00 - $ 494.00
$ 494.00
$ 395.00
$ 395.00 - $ 395.00
$ 395.00
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 %
$ 498.00
$ 498.00 - $ 498.00
$ 498.00
$ 399.00
$ 399.00 - $ 399.00
$ 399.00

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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$ 498.00
$ 498.00 - $ 498.00
$ 498.00
$ 399.00
$ 399.00 - $ 399.00
$ 399.00
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 %
$ 427.00
$ 427.00 - $ 427.00
$ 427.00
$ 342.00
$ 342.00 - $ 342.00
$ 342.00

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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$ 427.00
$ 427.00 - $ 427.00
$ 427.00
$ 342.00
$ 342.00 - $ 342.00
$ 342.00
Save 20% Save %

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