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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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$ 10.39
$ 10.39 - $ 10.39
$ 10.39
$ 8.29
$ 8.29 - $ 8.29
$ 8.29

Foster 47-4, 4 Series, Industrial Plug, 5/16" Hose Barb, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 47-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 10.39
$ 10.39 - $ 10.39
$ 10.39
$ 8.29
$ 8.29 - $ 8.29
$ 8.29
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$ 6.39
$ 6.39 - $ 6.39
$ 6.39
$ 5.09
$ 5.09 - $ 5.09
$ 5.09

Foster 71-4, 4 Series, Industrial Plug, 3/8" Push-On Hose Barb, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 71-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 6.39
$ 6.39 - $ 6.39
$ 6.39
$ 5.09
$ 5.09 - $ 5.09
$ 5.09
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$ 6.99
$ 6.99 - $ 6.99
$ 6.99
$ 5.59
$ 5.59 - $ 5.59
$ 5.59

Foster 49-4, 4 Series, Industrial Plug, 1/2" Hose Barb, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 49-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 6.99
$ 6.99 - $ 6.99
$ 6.99
$ 5.59
$ 5.59 - $ 5.59
$ 5.59
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$ 25.19
$ 25.19 - $ 25.19
$ 25.19
$ 20.09
$ 20.09 - $ 20.09
$ 20.09

Foster 4304, 4 Series, Industrial Coupler, Manual, 3/8" Male NPT, Brass, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4304 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 25.19
$ 25.19 - $ 25.19
$ 25.19
$ 20.09
$ 20.09 - $ 20.09
$ 20.09
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$ 31.79
$ 31.79 - $ 31.79
$ 31.79
$ 25.39
$ 25.39 - $ 25.39
$ 25.39

Foster FM4604, 4 Series, Industrial Coupler, Automatic, 1/4" Hose Barb, 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
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$ 11.39
$ 11.39 - $ 11.39
$ 11.39
$ 9.09
$ 9.09 - $ 9.09
$ 9.09

Foster 38-4, 4 Series, Industrial Plug, 1/8" Male NPT, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 38-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 11.39
$ 11.39 - $ 11.39
$ 11.39
$ 9.09
$ 9.09 - $ 9.09
$ 9.09
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Save 19% Save %
$ 7.39
$ 7.39 - $ 7.39
$ 7.39
$ 5.99
$ 5.99 - $ 5.99
$ 5.99

Foster 51-4, 4 Series, Industrial Plug, 1/4" Push-On Hose Barb, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 51-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 7.39
$ 7.39 - $ 7.39
$ 7.39
$ 5.99
$ 5.99 - $ 5.99
$ 5.99
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$ 26.89
$ 26.89 - $ 26.89
$ 26.89
$ 21.49
$ 21.49 - $ 21.49
$ 21.49

Foster 71-4B, 4 Series, Industrial Plug, 3/8" Push-On Hose Barb, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 71-4B is a Brass 3/8" industrial plug from the Foster 4 Series — a high-fl...

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$ 26.89
$ 26.89 - $ 26.89
$ 26.89
$ 21.49
$ 21.49 - $ 21.49
$ 21.49
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$ 10.79
$ 10.79 - $ 10.79
$ 10.79
$ 8.69
$ 8.69 - $ 8.69
$ 8.69

Foster 81-4, 4 Series, Industrial Plug, 1/2" Push-On Hose Barb, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 81-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 10.79
$ 10.79 - $ 10.79
$ 10.79
$ 8.69
$ 8.69 - $ 8.69
$ 8.69
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 27.39
$ 27.39 - $ 27.39
$ 27.39
$ 21.89
$ 21.89 - $ 21.89
$ 21.89

Foster 4604, 4 Series, Industrial Coupler, Manual, 1/4" Hose Barb, Brass, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4604 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 27.39
$ 27.39 - $ 27.39
$ 27.39
$ 21.89
$ 21.89 - $ 21.89
$ 21.89
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$ 28.79
$ 28.79 - $ 28.79
$ 28.79
$ 22.99
$ 22.99 - $ 22.99
$ 22.99

Foster 4704, 4 Series, Industrial Coupler, Manual, 5/16" Hose Barb, Brass, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4704 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 28.79
$ 28.79 - $ 28.79
$ 28.79
$ 22.99
$ 22.99 - $ 22.99
$ 22.99
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$ 28.19
$ 28.19 - $ 28.19
$ 28.19
$ 22.59
$ 22.59 - $ 22.59
$ 22.59

Foster 4804, 4 Series, Industrial Coupler, Manual, 3/8" Hose Barb, Brass, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4804 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 28.19
$ 28.19 - $ 28.19
$ 28.19
$ 22.59
$ 22.59 - $ 22.59
$ 22.59
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$ 27.39
$ 27.39 - $ 27.39
$ 27.39
$ 21.89
$ 21.89 - $ 21.89
$ 21.89

Foster 4904, 4 Series, Industrial Coupler, Manual, 1/2" Hose Barb, Brass, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4904 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 27.39
$ 27.39 - $ 27.39
$ 27.39
$ 21.89
$ 21.89 - $ 21.89
$ 21.89
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$ 24.99
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$ 24.99
$ 19.99
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$ 19.99

Foster 1714, 4 Series, Industrial Coupler, Manual, 3/8" Hose Barb (Push-On), Brass, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 1714 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 24.99
$ 24.99 - $ 24.99
$ 24.99
$ 19.99
$ 19.99 - $ 19.99
$ 19.99
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$ 27.49
$ 27.49 - $ 27.49
$ 27.49
$ 21.99
$ 21.99 - $ 21.99
$ 21.99

Foster 1814, 4 Series, Industrial Coupler, Manual, 1/2" Hose Barb (Push-On), Brass, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 1814 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 27.49
$ 27.49 - $ 27.49
$ 27.49
$ 21.99
$ 21.99 - $ 21.99
$ 21.99
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$ 32.19
$ 32.19 - $ 32.19
$ 32.19
$ 25.79
$ 25.79 - $ 25.79
$ 25.79

Foster FM4704, 4 Series, Industrial Coupler, Automatic, 5/16" Hose Barb, 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
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$ 35.89
$ 35.89 - $ 35.89
$ 35.89
$ 28.69
$ 28.69 - $ 28.69
$ 28.69

Foster FM1814, 4 Series, Industrial Coupler, Manual, 1/2" Hose Barb (Push-On), Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM1814 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 35.89
$ 35.89 - $ 35.89
$ 35.89
$ 28.69
$ 28.69 - $ 28.69
$ 28.69
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 20.39
$ 20.39 - $ 20.39
$ 20.39
$ 16.29
$ 16.29 - $ 16.29
$ 16.29

Foster PD13-4, 3/8" Industrial Plug x Reusable Hose Fitting, 3/8" ID x 13/16" OD, 4 Series, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster PD13-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-f...

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$ 20.39
$ 20.39 - $ 20.39
$ 20.39
$ 16.29
$ 16.29 - $ 16.29
$ 16.29
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 15.69
$ 15.69 - $ 15.69
$ 15.69
$ 12.59
$ 12.59 - $ 12.59
$ 12.59

Foster PD11-4, 3/8" Industrial Plug x Reusable Hose Fitting, 3/8" ID x 3/4" OD, 4 Series, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster PD11-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-f...

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$ 15.69
$ 15.69 - $ 15.69
$ 15.69
$ 12.59
$ 12.59 - $ 12.59
$ 12.59
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 14.39
$ 14.39 - $ 14.39
$ 14.39
$ 11.49
$ 11.49 - $ 11.49
$ 11.49

Foster PD9-4, 3/8" Industrial Plug x Reusable Hose Fitting, 3/8" ID x 11/16" OD, 4 Series, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster PD9-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-fl...

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$ 14.39
$ 14.39 - $ 14.39
$ 14.39
$ 11.49
$ 11.49 - $ 11.49
$ 11.49
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 14.29
$ 14.29 - $ 14.29
$ 14.29
$ 11.39
$ 11.39 - $ 11.39
$ 11.39

Foster PD7-4, 3/8" Industrial Plug x Reusable Hose Fitting, 3/8" ID x 5/8" OD, 4 Series, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster PD7-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-fl...

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$ 14.29
$ 14.29 - $ 14.29
$ 14.29
$ 11.39
$ 11.39 - $ 11.39
$ 11.39
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 %
$ 15.79
$ 15.79 - $ 15.79
$ 15.79
$ 12.69
$ 12.69 - $ 12.69
$ 12.69

Foster PB7-4, 3/8" Industrial Plug x Reusable Hose Fitting, 1/4" ID x 5/8" OD, 4 Series, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster PB7-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-fl...

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$ 15.79
$ 15.79 - $ 15.79
$ 15.79
$ 12.69
$ 12.69 - $ 12.69
$ 12.69
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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 13.89
$ 13.89 - $ 13.89
$ 13.89
$ 11.09
$ 11.09 - $ 11.09
$ 11.09

Foster PB5-4, 3/8" Industrial Plug x Reusable Hose Fitting, 1/4" ID x 9/16" OD, 4 Series, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster PB5-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-fl...

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$ 13.89
$ 13.89 - $ 13.89
$ 13.89
$ 11.09
$ 11.09 - $ 11.09
$ 11.09
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 %
$ 14.89
$ 14.89 - $ 14.89
$ 14.89
$ 11.89
$ 11.89 - $ 11.89
$ 11.89

Foster PB3-4, 3/8" Industrial Plug x Reusable Hose Fitting, 1/4" ID x 1/2" OD, 4 Series, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster PB3-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-fl...

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$ 14.89
$ 14.89 - $ 14.89
$ 14.89
$ 11.89
$ 11.89 - $ 11.89
$ 11.89
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