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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 %
$ 38.29
$ 38.29 - $ 38.29
$ 38.29
$ 30.59
$ 30.59 - $ 30.59
$ 30.59

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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$ 38.29
$ 38.29 - $ 38.29
$ 38.29
$ 30.59
$ 30.59 - $ 30.59
$ 30.59
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 %
$ 32.79
$ 32.79 - $ 32.79
$ 32.79
$ 26.19
$ 26.19 - $ 26.19
$ 26.19

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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$ 32.79
$ 32.79 - $ 32.79
$ 32.79
$ 26.19
$ 26.19 - $ 26.19
$ 26.19
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 %
$ 37.89
$ 37.89 - $ 37.89
$ 37.89
$ 30.29
$ 30.29 - $ 30.29
$ 30.29

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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$ 37.89
$ 37.89 - $ 37.89
$ 37.89
$ 30.29
$ 30.29 - $ 30.29
$ 30.29
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 %
$ 32.19
$ 32.19 - $ 32.19
$ 32.19
$ 25.79
$ 25.79 - $ 25.79
$ 25.79

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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$ 32.19
$ 32.19 - $ 32.19
$ 32.19
$ 25.79
$ 25.79 - $ 25.79
$ 25.79
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 %
$ 37.29
$ 37.29 - $ 37.29
$ 37.29
$ 29.79
$ 29.79 - $ 29.79
$ 29.79

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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$ 37.29
$ 37.29 - $ 37.29
$ 37.29
$ 29.79
$ 29.79 - $ 29.79
$ 29.79
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 %
$ 31.79
$ 31.79 - $ 31.79
$ 31.79
$ 25.39
$ 25.39 - $ 25.39
$ 25.39

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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$ 31.79
$ 31.79 - $ 31.79
$ 31.79
$ 25.39
$ 25.39 - $ 25.39
$ 25.39
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 %
$ 36.69
$ 36.69 - $ 36.69
$ 36.69
$ 29.29
$ 29.29 - $ 29.29
$ 29.29

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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$ 36.69
$ 36.69 - $ 36.69
$ 36.69
$ 29.29
$ 29.29 - $ 29.29
$ 29.29
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 %
$ 38.69
$ 38.69 - $ 38.69
$ 38.69
$ 30.99
$ 30.99 - $ 30.99
$ 30.99

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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$ 38.69
$ 38.69 - $ 38.69
$ 38.69
$ 30.99
$ 30.99 - $ 30.99
$ 30.99
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 %
$ 38.29
$ 38.29 - $ 38.29
$ 38.29
$ 30.59
$ 30.59 - $ 30.59
$ 30.59

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...

View full details
$ 38.29
$ 38.29 - $ 38.29
$ 38.29
$ 30.59
$ 30.59 - $ 30.59
$ 30.59
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 %
$ 32.39
$ 32.39 - $ 32.39
$ 32.39
$ 25.89
$ 25.89 - $ 25.89
$ 25.89

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...

View full details
$ 32.39
$ 32.39 - $ 32.39
$ 32.39
$ 25.89
$ 25.89 - $ 25.89
$ 25.89
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 %
$ 37.69
$ 37.69 - $ 37.69
$ 37.69
$ 30.09
$ 30.09 - $ 30.09
$ 30.09

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...

View full details
$ 37.69
$ 37.69 - $ 37.69
$ 37.69
$ 30.09
$ 30.09 - $ 30.09
$ 30.09
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 %
$ 36.89
$ 36.89 - $ 36.89
$ 36.89
$ 29.49
$ 29.49 - $ 29.49
$ 29.49

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...

View full details
$ 36.89
$ 36.89 - $ 36.89
$ 36.89
$ 29.49
$ 29.49 - $ 29.49
$ 29.49
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 %
$ 36.49
$ 36.49 - $ 36.49
$ 36.49
$ 29.19
$ 29.19 - $ 29.19
$ 29.19

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
$ 36.49
$ 36.49 - $ 36.49
$ 36.49
$ 29.19
$ 29.19 - $ 29.19
$ 29.19
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 %
$ 31.99
$ 31.99 - $ 31.99
$ 31.99
$ 25.59
$ 25.59 - $ 25.59
$ 25.59

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
$ 31.99
$ 31.99 - $ 31.99
$ 31.99
$ 25.59
$ 25.59 - $ 25.59
$ 25.59
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 %
$ 35.59
$ 35.59 - $ 35.59
$ 35.59
$ 28.49
$ 28.49 - $ 28.49
$ 28.49

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...

View full details
$ 35.59
$ 35.59 - $ 35.59
$ 35.59
$ 28.49
$ 28.49 - $ 28.49
$ 28.49
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 %
$ 36.49
$ 36.49 - $ 36.49
$ 36.49
$ 29.19
$ 29.19 - $ 29.19
$ 29.19

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
$ 36.49
$ 36.49 - $ 36.49
$ 36.49
$ 29.19
$ 29.19 - $ 29.19
$ 29.19
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 %
$ 37.29
$ 37.29 - $ 37.29
$ 37.29
$ 29.79
$ 29.79 - $ 29.79
$ 29.79

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
$ 37.29
$ 37.29 - $ 37.29
$ 37.29
$ 29.79
$ 29.79 - $ 29.79
$ 29.79
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 %
$ 31.79
$ 31.79 - $ 31.79
$ 31.79
$ 25.39
$ 25.39 - $ 25.39
$ 25.39

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
$ 31.79
$ 31.79 - $ 31.79
$ 31.79
$ 25.39
$ 25.39 - $ 25.39
$ 25.39
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 %
$ 38.09
$ 38.09 - $ 38.09
$ 38.09
$ 30.49
$ 30.49 - $ 30.49
$ 30.49

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
$ 38.09
$ 38.09 - $ 38.09
$ 38.09
$ 30.49
$ 30.49 - $ 30.49
$ 30.49
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 %
$ 37.29
$ 37.29 - $ 37.29
$ 37.29
$ 29.79
$ 29.79 - $ 29.79
$ 29.79

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
$ 37.29
$ 37.29 - $ 37.29
$ 37.29
$ 29.79
$ 29.79 - $ 29.79
$ 29.79
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 %
$ 38.29
$ 38.29 - $ 38.29
$ 38.29
$ 30.59
$ 30.59 - $ 30.59
$ 30.59

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
$ 38.29
$ 38.29 - $ 38.29
$ 38.29
$ 30.59
$ 30.59 - $ 30.59
$ 30.59
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 %
$ 32.79
$ 32.79 - $ 32.79
$ 32.79
$ 26.19
$ 26.19 - $ 26.19
$ 26.19

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
$ 32.79
$ 32.79 - $ 32.79
$ 32.79
$ 26.19
$ 26.19 - $ 26.19
$ 26.19
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 %
$ 37.69
$ 37.69 - $ 37.69
$ 37.69
$ 30.09
$ 30.09 - $ 30.09
$ 30.09

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
$ 37.69
$ 37.69 - $ 37.69
$ 37.69
$ 30.09
$ 30.09 - $ 30.09
$ 30.09
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 %
$ 32.69
$ 32.69 - $ 32.69
$ 32.69
$ 26.19
$ 26.19 - $ 26.19
$ 26.19

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...

View full details
$ 32.69
$ 32.69 - $ 32.69
$ 32.69
$ 26.19
$ 26.19 - $ 26.19
$ 26.19
Save 20% Save %

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