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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 %
$ 656.00
$ 656.00 - $ 656.00
$ 656.00
$ 525.00
$ 525.00 - $ 525.00
$ 525.00

Foster FM4804H, 3/8" Industrial Coupler x 3/8" Hose ID, 4 Series, Automatic, Heat/Viton, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4804H is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 656.00
$ 656.00 - $ 656.00
$ 656.00
$ 525.00
$ 525.00 - $ 525.00
$ 525.00
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 %
$ 726.00
$ 726.00 - $ 726.00
$ 726.00
$ 580.00
$ 580.00 - $ 580.00
$ 580.00

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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$ 726.00
$ 726.00 - $ 726.00
$ 726.00
$ 580.00
$ 580.00 - $ 580.00
$ 580.00
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 %
$ 622.00
$ 622.00 - $ 622.00
$ 622.00
$ 497.00
$ 497.00 - $ 497.00
$ 497.00

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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$ 622.00
$ 622.00 - $ 622.00
$ 622.00
$ 497.00
$ 497.00 - $ 497.00
$ 497.00
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 %
$ 718.00
$ 718.00 - $ 718.00
$ 718.00
$ 574.00
$ 574.00 - $ 574.00
$ 574.00

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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$ 718.00
$ 718.00 - $ 718.00
$ 718.00
$ 574.00
$ 574.00 - $ 574.00
$ 574.00
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 %
$ 610.00
$ 610.00 - $ 610.00
$ 610.00
$ 489.00
$ 489.00 - $ 489.00
$ 489.00

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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$ 610.00
$ 610.00 - $ 610.00
$ 610.00
$ 489.00
$ 489.00 - $ 489.00
$ 489.00
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 %
$ 707.00
$ 707.00 - $ 707.00
$ 707.00
$ 565.00
$ 565.00 - $ 565.00
$ 565.00

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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$ 707.00
$ 707.00 - $ 707.00
$ 707.00
$ 565.00
$ 565.00 - $ 565.00
$ 565.00
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 %
$ 603.00
$ 603.00 - $ 603.00
$ 603.00
$ 481.00
$ 481.00 - $ 481.00
$ 481.00

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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$ 603.00
$ 603.00 - $ 603.00
$ 603.00
$ 481.00
$ 481.00 - $ 481.00
$ 481.00
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 %
$ 695.00
$ 695.00 - $ 695.00
$ 695.00
$ 555.00
$ 555.00 - $ 555.00
$ 555.00

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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$ 695.00
$ 695.00 - $ 695.00
$ 695.00
$ 555.00
$ 555.00 - $ 555.00
$ 555.00
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 %
$ 733.00
$ 733.00 - $ 733.00
$ 733.00
$ 588.00
$ 588.00 - $ 588.00
$ 588.00

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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$ 733.00
$ 733.00 - $ 733.00
$ 733.00
$ 588.00
$ 588.00 - $ 588.00
$ 588.00
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 %
$ 726.00
$ 726.00 - $ 726.00
$ 726.00
$ 580.00
$ 580.00 - $ 580.00
$ 580.00

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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$ 726.00
$ 726.00 - $ 726.00
$ 726.00
$ 580.00
$ 580.00 - $ 580.00
$ 580.00
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 %
$ 614.00
$ 614.00 - $ 614.00
$ 614.00
$ 491.00
$ 491.00 - $ 491.00
$ 491.00

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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$ 614.00
$ 614.00 - $ 614.00
$ 614.00
$ 491.00
$ 491.00 - $ 491.00
$ 491.00
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 %
$ 714.00
$ 714.00 - $ 714.00
$ 714.00
$ 570.00
$ 570.00 - $ 570.00
$ 570.00

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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$ 714.00
$ 714.00 - $ 714.00
$ 714.00
$ 570.00
$ 570.00 - $ 570.00
$ 570.00
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 %
$ 699.00
$ 699.00 - $ 699.00
$ 699.00
$ 559.00
$ 559.00 - $ 559.00
$ 559.00

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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$ 699.00
$ 699.00 - $ 699.00
$ 699.00
$ 559.00
$ 559.00 - $ 559.00
$ 559.00
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 %
$ 606.00
$ 606.00 - $ 606.00
$ 606.00
$ 485.00
$ 485.00 - $ 485.00
$ 485.00

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...

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$ 606.00
$ 606.00 - $ 606.00
$ 606.00
$ 485.00
$ 485.00 - $ 485.00
$ 485.00
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 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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$ 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 %
$ 692.00
$ 692.00 - $ 692.00
$ 692.00
$ 553.00
$ 553.00 - $ 553.00
$ 553.00

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...

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$ 692.00
$ 692.00 - $ 692.00
$ 692.00
$ 553.00
$ 553.00 - $ 553.00
$ 553.00
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 %
$ 707.00
$ 707.00 - $ 707.00
$ 707.00
$ 565.00
$ 565.00 - $ 565.00
$ 565.00

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...

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$ 707.00
$ 707.00 - $ 707.00
$ 707.00
$ 565.00
$ 565.00 - $ 565.00
$ 565.00
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 %
$ 603.00
$ 603.00 - $ 603.00
$ 603.00
$ 481.00
$ 481.00 - $ 481.00
$ 481.00

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
$ 603.00
$ 603.00 - $ 603.00
$ 603.00
$ 481.00
$ 481.00 - $ 481.00
$ 481.00
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 %
$ 722.00
$ 722.00 - $ 722.00
$ 722.00
$ 578.00
$ 578.00 - $ 578.00
$ 578.00

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...

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$ 722.00
$ 722.00 - $ 722.00
$ 722.00
$ 578.00
$ 578.00 - $ 578.00
$ 578.00
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 %
$ 707.00
$ 707.00 - $ 707.00
$ 707.00
$ 565.00
$ 565.00 - $ 565.00
$ 565.00

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...

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$ 707.00
$ 707.00 - $ 707.00
$ 707.00
$ 565.00
$ 565.00 - $ 565.00
$ 565.00
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 %
$ 726.00
$ 726.00 - $ 726.00
$ 726.00
$ 580.00
$ 580.00 - $ 580.00
$ 580.00

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
$ 726.00
$ 726.00 - $ 726.00
$ 726.00
$ 580.00
$ 580.00 - $ 580.00
$ 580.00
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 %
$ 622.00
$ 622.00 - $ 622.00
$ 622.00
$ 497.00
$ 497.00 - $ 497.00
$ 497.00

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
$ 622.00
$ 622.00 - $ 622.00
$ 622.00
$ 497.00
$ 497.00 - $ 497.00
$ 497.00
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 %
$ 714.00
$ 714.00 - $ 714.00
$ 714.00
$ 570.00
$ 570.00 - $ 570.00
$ 570.00

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...

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$ 714.00
$ 714.00 - $ 714.00
$ 714.00
$ 570.00
$ 570.00 - $ 570.00
$ 570.00
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 %
$ 620.00
$ 620.00 - $ 620.00
$ 620.00
$ 497.00
$ 497.00 - $ 497.00
$ 497.00

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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$ 620.00
$ 620.00 - $ 620.00
$ 620.00
$ 497.00
$ 497.00 - $ 497.00
$ 497.00
Save 20% Save %

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