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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 %
$ 33.19
$ 33.19 - $ 33.19
$ 33.19
$ 26.59
$ 26.59 - $ 26.59
$ 26.59

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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$ 33.19
$ 33.19 - $ 33.19
$ 33.19
$ 26.59
$ 26.59 - $ 26.59
$ 26.59
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 %
$ 27.99
$ 27.99 - $ 27.99
$ 27.99
$ 22.39
$ 22.39 - $ 22.39
$ 22.39

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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$ 27.99
$ 27.99 - $ 27.99
$ 27.99
$ 22.39
$ 22.39 - $ 22.39
$ 22.39
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 %
$ 29.49
$ 29.49 - $ 29.49
$ 29.49
$ 23.59
$ 23.59 - $ 23.59
$ 23.59

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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$ 29.49
$ 29.49 - $ 29.49
$ 29.49
$ 23.59
$ 23.59 - $ 23.59
$ 23.59
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 %
$ 51.89
$ 51.89 - $ 51.89
$ 51.89
$ 41.49
$ 41.49 - $ 41.49
$ 41.49

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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$ 51.89
$ 51.89 - $ 51.89
$ 51.89
$ 41.49
$ 41.49 - $ 41.49
$ 41.49
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 %
$ 48.89
$ 48.89 - $ 48.89
$ 48.89
$ 39.09
$ 39.09 - $ 39.09
$ 39.09

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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$ 48.89
$ 48.89 - $ 48.89
$ 48.89
$ 39.09
$ 39.09 - $ 39.09
$ 39.09
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 %
$ 30.19
$ 30.19 - $ 30.19
$ 30.19
$ 24.09
$ 24.09 - $ 24.09
$ 24.09

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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$ 30.19
$ 30.19 - $ 30.19
$ 30.19
$ 24.09
$ 24.09 - $ 24.09
$ 24.09
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 %
$ 29.09
$ 29.09 - $ 29.09
$ 29.09
$ 23.29
$ 23.29 - $ 23.29
$ 23.29

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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$ 29.09
$ 29.09 - $ 29.09
$ 29.09
$ 23.29
$ 23.29 - $ 23.29
$ 23.29
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 %
$ 28.89
$ 28.89 - $ 28.89
$ 28.89
$ 23.09
$ 23.09 - $ 23.09
$ 23.09

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 —...

View full details
$ 28.89
$ 28.89 - $ 28.89
$ 28.89
$ 23.09
$ 23.09 - $ 23.09
$ 23.09
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 %
$ 24.19
$ 24.19 - $ 24.19
$ 24.19
$ 19.39
$ 19.39 - $ 19.39
$ 19.39

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...

View full details
$ 24.19
$ 24.19 - $ 24.19
$ 24.19
$ 19.39
$ 19.39 - $ 19.39
$ 19.39
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 %
$ 28.09
$ 28.09 - $ 28.09
$ 28.09
$ 22.49
$ 22.49 - $ 22.49
$ 22.49

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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$ 28.09
$ 28.09 - $ 28.09
$ 28.09
$ 22.49
$ 22.49 - $ 22.49
$ 22.49
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 %
$ 23.39
$ 23.39 - $ 23.39
$ 23.39
$ 18.79
$ 18.79 - $ 18.79
$ 18.79

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...

View full details
$ 23.39
$ 23.39 - $ 23.39
$ 23.39
$ 18.79
$ 18.79 - $ 18.79
$ 18.79
Save 20% Save %

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