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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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$ 198.00
$ 198.00 - $ 198.00
$ 198.00
$ 158.00
$ 158.00 - $ 158.00
$ 158.00

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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$ 198.00
$ 198.00 - $ 198.00
$ 198.00
$ 158.00
$ 158.00 - $ 158.00
$ 158.00
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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 %
$ 95.00
$ 95.00 - $ 95.00
$ 95.00
$ 76.00
$ 76.00 - $ 76.00
$ 76.00

Foster 42-4, 3/8" Industrial Plug x 3/8" Male NPT, 4 Series, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 42-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 95.00
$ 95.00 - $ 95.00
$ 95.00
$ 76.00
$ 76.00 - $ 76.00
$ 76.00
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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 %
$ 695.00
$ 695.00 - $ 695.00
$ 695.00
$ 556.00
$ 556.00 - $ 556.00
$ 556.00

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...

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$ 695.00
$ 695.00 - $ 695.00
$ 695.00
$ 556.00
$ 556.00 - $ 556.00
$ 556.00
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$ 122.00
$ 122.00 - $ 122.00
$ 122.00
$ 97.00
$ 97.00 - $ 97.00
$ 97.00

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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$ 122.00
$ 122.00 - $ 122.00
$ 122.00
$ 97.00
$ 97.00 - $ 97.00
$ 97.00
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$ 134.00
$ 134.00 - $ 134.00
$ 134.00
$ 107.00
$ 107.00 - $ 107.00
$ 107.00

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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$ 134.00
$ 134.00 - $ 134.00
$ 134.00
$ 107.00
$ 107.00 - $ 107.00
$ 107.00
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$ 480.00
$ 480.00 - $ 480.00
$ 480.00
$ 383.00
$ 383.00 - $ 383.00
$ 383.00

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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$ 480.00
$ 480.00 - $ 480.00
$ 480.00
$ 383.00
$ 383.00 - $ 383.00
$ 383.00
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$ 606.00
$ 606.00 - $ 606.00
$ 606.00
$ 484.00
$ 484.00 - $ 484.00
$ 484.00

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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$ 606.00
$ 606.00 - $ 606.00
$ 606.00
$ 484.00
$ 484.00 - $ 484.00
$ 484.00
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$ 217.00
$ 217.00 - $ 217.00
$ 217.00
$ 174.00
$ 174.00 - $ 174.00
$ 174.00

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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$ 217.00
$ 217.00 - $ 217.00
$ 217.00
$ 174.00
$ 174.00 - $ 174.00
$ 174.00
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$ 141.00
$ 141.00 - $ 141.00
$ 141.00
$ 115.00
$ 115.00 - $ 115.00
$ 115.00

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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$ 141.00
$ 141.00 - $ 141.00
$ 141.00
$ 115.00
$ 115.00 - $ 115.00
$ 115.00
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$ 512.00
$ 512.00 - $ 512.00
$ 512.00
$ 410.00
$ 410.00 - $ 410.00
$ 410.00

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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$ 512.00
$ 512.00 - $ 512.00
$ 512.00
$ 410.00
$ 410.00 - $ 410.00
$ 410.00
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Save 19% Save %
$ 206.00
$ 206.00 - $ 206.00
$ 206.00
$ 166.00
$ 166.00 - $ 166.00
$ 166.00

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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$ 206.00
$ 206.00 - $ 206.00
$ 206.00
$ 166.00
$ 166.00 - $ 166.00
$ 166.00
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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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$ 522.00
$ 522.00 - $ 522.00
$ 522.00
$ 417.00
$ 417.00 - $ 417.00
$ 417.00

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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$ 522.00
$ 522.00 - $ 522.00
$ 522.00
$ 417.00
$ 417.00 - $ 417.00
$ 417.00
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$ 548.00
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$ 548.00
$ 438.00
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$ 438.00

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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$ 548.00
$ 548.00 - $ 548.00
$ 548.00
$ 438.00
$ 438.00 - $ 438.00
$ 438.00
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$ 537.00
$ 537.00 - $ 537.00
$ 537.00
$ 430.00
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$ 430.00

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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$ 537.00
$ 537.00 - $ 537.00
$ 537.00
$ 430.00
$ 430.00 - $ 430.00
$ 430.00
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$ 522.00
$ 522.00 - $ 522.00
$ 522.00
$ 417.00
$ 417.00 - $ 417.00
$ 417.00

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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$ 522.00
$ 522.00 - $ 522.00
$ 522.00
$ 417.00
$ 417.00 - $ 417.00
$ 417.00
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$ 476.00
$ 476.00 - $ 476.00
$ 476.00
$ 381.00
$ 381.00 - $ 381.00
$ 381.00

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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$ 476.00
$ 476.00 - $ 476.00
$ 476.00
$ 381.00
$ 381.00 - $ 381.00
$ 381.00
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$ 524.00
$ 524.00 - $ 524.00
$ 524.00
$ 419.00
$ 419.00 - $ 419.00
$ 419.00

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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$ 524.00
$ 524.00 - $ 524.00
$ 524.00
$ 419.00
$ 419.00 - $ 419.00
$ 419.00
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$ 613.00
$ 613.00 - $ 613.00
$ 613.00
$ 491.00
$ 491.00 - $ 491.00
$ 491.00

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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$ 613.00
$ 613.00 - $ 613.00
$ 613.00
$ 491.00
$ 491.00 - $ 491.00
$ 491.00
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$ 684.00
$ 684.00 - $ 684.00
$ 684.00
$ 547.00
$ 547.00 - $ 547.00
$ 547.00

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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$ 684.00
$ 684.00 - $ 684.00
$ 684.00
$ 547.00
$ 547.00 - $ 547.00
$ 547.00
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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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$ 389.00
$ 389.00 - $ 389.00
$ 389.00
$ 311.00
$ 311.00 - $ 311.00
$ 311.00

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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$ 389.00
$ 389.00 - $ 389.00
$ 389.00
$ 311.00
$ 311.00 - $ 311.00
$ 311.00
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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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$ 299.00
$ 299.00 - $ 299.00
$ 299.00
$ 240.00
$ 240.00 - $ 240.00
$ 240.00

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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$ 299.00
$ 299.00 - $ 299.00
$ 299.00
$ 240.00
$ 240.00 - $ 240.00
$ 240.00
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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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$ 274.00
$ 274.00 - $ 274.00
$ 274.00
$ 219.00
$ 219.00 - $ 219.00
$ 219.00

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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$ 274.00
$ 274.00 - $ 274.00
$ 274.00
$ 219.00
$ 219.00 - $ 219.00
$ 219.00
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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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$ 272.00
$ 272.00 - $ 272.00
$ 272.00
$ 217.00
$ 217.00 - $ 217.00
$ 217.00

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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$ 272.00
$ 272.00 - $ 272.00
$ 272.00
$ 217.00
$ 217.00 - $ 217.00
$ 217.00
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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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$ 301.00
$ 301.00 - $ 301.00
$ 301.00
$ 242.00
$ 242.00 - $ 242.00
$ 242.00

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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$ 301.00
$ 301.00 - $ 301.00
$ 301.00
$ 242.00
$ 242.00 - $ 242.00
$ 242.00
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