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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 %
$ 630.00
$ 630.00 - $ 630.00
$ 630.00
$ 505.00
$ 505.00 - $ 505.00
$ 505.00

Foster BL4404, 3/8" Industrial Coupler x 1/2" Female NPT, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4404 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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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 %
$ 531.00
$ 531.00 - $ 531.00
$ 531.00
$ 425.00
$ 425.00 - $ 425.00
$ 425.00

Foster 4404, 3/8" Industrial Coupler x 1/2" Female NPT, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4404 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 531.00
$ 531.00 - $ 531.00
$ 531.00
$ 425.00
$ 425.00 - $ 425.00
$ 425.00
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 %
$ 560.00
$ 560.00 - $ 560.00
$ 560.00
$ 448.00
$ 448.00 - $ 448.00
$ 448.00

Foster 4204W, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4204W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 560.00
$ 560.00 - $ 560.00
$ 560.00
$ 448.00
$ 448.00 - $ 448.00
$ 448.00
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 %
$ 985.00
$ 985.00 - $ 985.00
$ 985.00
$ 788.00
$ 788.00 - $ 788.00
$ 788.00

Foster BL4204S/S, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, Ball Lock, 303 Stainless

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4204S/S is a 303 Stainless 3/8" industrial coupler from the Foster 4 Ser...

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$ 985.00
$ 985.00 - $ 985.00
$ 985.00
$ 788.00
$ 788.00 - $ 788.00
$ 788.00
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 %
$ 928.00
$ 928.00 - $ 928.00
$ 928.00
$ 742.00
$ 742.00 - $ 742.00
$ 742.00

Foster 4204S/S, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, 303 Stainless

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4204S/S is a 303 Stainless 3/8" industrial coupler from the Foster 4 Serie...

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$ 928.00
$ 928.00 - $ 928.00
$ 928.00
$ 742.00
$ 742.00 - $ 742.00
$ 742.00
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 %
$ 573.00
$ 573.00 - $ 573.00
$ 573.00
$ 457.00
$ 457.00 - $ 457.00
$ 457.00

Foster 4204S, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, Steam/EPDM, Brass body, Brass sleeve, SS valve

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4204S is a Brass body, Brass sleeve, SS valve 3/8" industrial coupler from...

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$ 573.00
$ 573.00 - $ 573.00
$ 573.00
$ 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 %
$ 552.00
$ 552.00 - $ 552.00
$ 552.00
$ 442.00
$ 442.00 - $ 442.00
$ 442.00

Foster 4204H, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, Heat/Viton, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4204H is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — ...

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$ 552.00
$ 552.00 - $ 552.00
$ 552.00
$ 442.00
$ 442.00 - $ 442.00
$ 442.00
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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 %
$ 549.00
$ 549.00 - $ 549.00
$ 549.00
$ 438.00
$ 438.00 - $ 438.00
$ 438.00

Foster BL4204, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4204 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 549.00
$ 549.00 - $ 549.00
$ 549.00
$ 438.00
$ 438.00 - $ 438.00
$ 438.00
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 %
$ 459.00
$ 459.00 - $ 459.00
$ 459.00
$ 368.00
$ 368.00 - $ 368.00
$ 368.00

Foster 4204, 3/8" Industrial Coupler x 3/8" Female NPT, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4204 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 459.00
$ 459.00 - $ 459.00
$ 459.00
$ 368.00
$ 368.00 - $ 368.00
$ 368.00
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 %
$ 533.00
$ 533.00 - $ 533.00
$ 533.00
$ 427.00
$ 427.00 - $ 427.00
$ 427.00

Foster BL4004, 3/8" Industrial Coupler x 1/4" Female NPT, 4 Series, Ball Lock, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster BL4004 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series —...

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$ 533.00
$ 533.00 - $ 533.00
$ 533.00
$ 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 %
$ 444.00
$ 444.00 - $ 444.00
$ 444.00
$ 357.00
$ 357.00 - $ 357.00
$ 357.00

Foster 4004, 3/8" Industrial Coupler x 1/4" Female NPT, 4 Series, Brass/Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4004 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 444.00
$ 444.00 - $ 444.00
$ 444.00
$ 357.00
$ 357.00 - $ 357.00
$ 357.00
Save 20% Save %

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