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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 %
$ 678.00
$ 678.00 - $ 678.00
$ 678.00
$ 542.00
$ 542.00 - $ 542.00
$ 542.00

Foster SL4804, 3/8" Industrial Coupler x 3/8" Hose ID, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL4804 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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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 %
$ 581.00
$ 581.00 - $ 581.00
$ 581.00
$ 464.00
$ 464.00 - $ 464.00
$ 464.00

Foster FM4804, 3/8" Industrial Coupler x 3/8" Hose ID, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4804 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 581.00
$ 581.00 - $ 581.00
$ 581.00
$ 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 Save 20% Save %
$ 671.00
$ 671.00 - $ 671.00
$ 671.00
$ 537.00
$ 537.00 - $ 537.00
$ 537.00

Foster SL4704, 3/8" Industrial Coupler x 5/16" Hose ID, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL4704 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 671.00
$ 671.00 - $ 671.00
$ 671.00
$ 537.00
$ 537.00 - $ 537.00
$ 537.00
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 %
$ 570.00
$ 570.00 - $ 570.00
$ 570.00
$ 457.00
$ 457.00 - $ 457.00
$ 457.00

Foster FM4704, 3/8" Industrial Coupler x 5/16" Hose ID, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4704 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 570.00
$ 570.00 - $ 570.00
$ 570.00
$ 457.00
$ 457.00 - $ 457.00
$ 457.00
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 %
$ 661.00
$ 661.00 - $ 661.00
$ 661.00
$ 528.00
$ 528.00 - $ 528.00
$ 528.00

Foster SL4604, 3/8" Industrial Coupler x 1/4" Hose ID, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL4604 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 661.00
$ 661.00 - $ 661.00
$ 661.00
$ 528.00
$ 528.00 - $ 528.00
$ 528.00
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 %
$ 563.00
$ 563.00 - $ 563.00
$ 563.00
$ 450.00
$ 450.00 - $ 450.00
$ 450.00

Foster FM4604, 3/8" Industrial Coupler x 1/4" Hose ID, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4604 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 563.00
$ 563.00 - $ 563.00
$ 563.00
$ 450.00
$ 450.00 - $ 450.00
$ 450.00
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 %
$ 650.00
$ 650.00 - $ 650.00
$ 650.00
$ 519.00
$ 519.00 - $ 519.00
$ 519.00

Foster FM4504W, 3/8" Industrial Coupler x 1/2" Male NPT, 4 Series, Automatic, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4504W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a...

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$ 650.00
$ 650.00 - $ 650.00
$ 650.00
$ 519.00
$ 519.00 - $ 519.00
$ 519.00
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 %
$ 685.00
$ 685.00 - $ 685.00
$ 685.00
$ 549.00
$ 549.00 - $ 549.00
$ 549.00

Foster FM4504S, 3/8" Industrial Coupler x 1/2" Male NPT, 4 Series, Automatic, Steam/EPDM, Brass body, Brass sleeve, SS valve

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4504S is a Brass body, Brass sleeve, SS valve 3/8" industrial coupler fr...

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$ 685.00
$ 685.00 - $ 685.00
$ 685.00
$ 549.00
$ 549.00 - $ 549.00
$ 549.00
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 SL4504, 3/8" Industrial Coupler x 1/2" Male NPT, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL4504 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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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 %
$ 574.00
$ 574.00 - $ 574.00
$ 574.00
$ 459.00
$ 459.00 - $ 459.00
$ 459.00

Foster FM4504, 3/8" Industrial Coupler x 1/2" Male NPT, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4504 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 574.00
$ 574.00 - $ 574.00
$ 574.00
$ 459.00
$ 459.00 - $ 459.00
$ 459.00
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 %
$ 668.00
$ 668.00 - $ 668.00
$ 668.00
$ 533.00
$ 533.00 - $ 533.00
$ 533.00

Foster FM4304W, 3/8" Industrial Coupler x 3/8" Male NPT, 4 Series, Automatic, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4304W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a...

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$ 668.00
$ 668.00 - $ 668.00
$ 668.00
$ 533.00
$ 533.00 - $ 533.00
$ 533.00
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 %
$ 653.00
$ 653.00 - $ 653.00
$ 653.00
$ 522.00
$ 522.00 - $ 522.00
$ 522.00

Foster FM4304S, 3/8" Industrial Coupler x 3/8" Male NPT, 4 Series, Automatic, Steam/EPDM, Brass body, Brass sleeve, SS valve

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4304S is a Brass body, Brass sleeve, SS valve 3/8" industrial coupler fr...

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$ 653.00
$ 653.00 - $ 653.00
$ 653.00
$ 522.00
$ 522.00 - $ 522.00
$ 522.00
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
$ 517.00
$ 517.00 - $ 517.00
$ 517.00

Foster SL4304, 3/8" Industrial Coupler x 3/8" Male NPT, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL4304 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

View full details
$ 646.00
$ 646.00 - $ 646.00
$ 646.00
$ 517.00
$ 517.00 - $ 517.00
$ 517.00
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 %
$ 567.00
$ 567.00 - $ 567.00
$ 567.00
$ 453.00
$ 453.00 - $ 453.00
$ 453.00

Foster FM4304, 3/8" Industrial Coupler x 3/8" Male NPT, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4304 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

View full details
$ 567.00
$ 567.00 - $ 567.00
$ 567.00
$ 453.00
$ 453.00 - $ 453.00
$ 453.00
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 %
$ 630.00
$ 630.00 - $ 630.00
$ 630.00
$ 505.00
$ 505.00 - $ 505.00
$ 505.00

Foster FM4104W, 3/8" Industrial Coupler x 1/4" Male NPT, 4 Series, Automatic, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4104W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a...

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$ 630.00
$ 630.00 - $ 630.00
$ 630.00
$ 505.00
$ 505.00 - $ 505.00
$ 505.00
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
$ 517.00
$ 517.00 - $ 517.00
$ 517.00

Foster FM4104S, 3/8" Industrial Coupler x 1/4" Male NPT, 4 Series, Automatic, Steam/EPDM, Brass body, Brass sleeve, SS valve

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4104S is a Brass body, Brass sleeve, SS valve 3/8" industrial coupler fr...

View full details
$ 646.00
$ 646.00 - $ 646.00
$ 646.00
$ 517.00
$ 517.00 - $ 517.00
$ 517.00
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 %
$ 661.00
$ 661.00 - $ 661.00
$ 661.00
$ 528.00
$ 528.00 - $ 528.00
$ 528.00

Foster SL4104, 3/8" Industrial Coupler x 1/4" Male NPT, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL4104 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

View full details
$ 661.00
$ 661.00 - $ 661.00
$ 661.00
$ 528.00
$ 528.00 - $ 528.00
$ 528.00
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 %
$ 563.00
$ 563.00 - $ 563.00
$ 563.00
$ 450.00
$ 450.00 - $ 450.00
$ 450.00

Foster FM4104, 3/8" Industrial Coupler x 1/4" Male NPT, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4104 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

View full details
$ 563.00
$ 563.00 - $ 563.00
$ 563.00
$ 450.00
$ 450.00 - $ 450.00
$ 450.00
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 %
$ 675.00
$ 675.00 - $ 675.00
$ 675.00
$ 540.00
$ 540.00 - $ 540.00
$ 540.00

Foster FM4404W, 3/8" Industrial Coupler x 1/2" Female NPT, 4 Series, Automatic, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4404W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a...

View full details
$ 675.00
$ 675.00 - $ 675.00
$ 675.00
$ 540.00
$ 540.00 - $ 540.00
$ 540.00
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 %
$ 661.00
$ 661.00 - $ 661.00
$ 661.00
$ 528.00
$ 528.00 - $ 528.00
$ 528.00

Foster FM4404S, 3/8" Industrial Coupler x 1/2" Female NPT, 4 Series, Automatic, Steam/EPDM, Brass body, Brass sleeve, SS valve

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4404S is a Brass body, Brass sleeve, SS valve 3/8" industrial coupler fr...

View full details
$ 661.00
$ 661.00 - $ 661.00
$ 661.00
$ 528.00
$ 528.00 - $ 528.00
$ 528.00
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 SL4404, 3/8" Industrial Coupler x 1/2" Female NPT, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL4404 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

View full details
$ 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 %
$ 581.00
$ 581.00 - $ 581.00
$ 581.00
$ 464.00
$ 464.00 - $ 464.00
$ 464.00

Foster FM4404, 3/8" Industrial Coupler x 1/2" Female NPT, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4404 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

View full details
$ 581.00
$ 581.00 - $ 581.00
$ 581.00
$ 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
Save 20% Save %
$ 668.00
$ 668.00 - $ 668.00
$ 668.00
$ 533.00
$ 533.00 - $ 533.00
$ 533.00

Foster FM4204W, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, Automatic, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4204W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a...

View full details
$ 668.00
$ 668.00 - $ 668.00
$ 668.00
$ 533.00
$ 533.00 - $ 533.00
$ 533.00
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 %
$ 579.00
$ 579.00 - $ 579.00
$ 579.00
$ 464.00
$ 464.00 - $ 464.00
$ 464.00

Foster FM4204H, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, Automatic, Heat/Viton, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4204H is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 579.00
$ 579.00 - $ 579.00
$ 579.00
$ 464.00
$ 464.00 - $ 464.00
$ 464.00
Save 20% Save %

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