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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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$ 197.00
$ 197.00 - $ 197.00
$ 197.00
$ 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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$ 197.00
$ 197.00 - $ 197.00
$ 197.00
$ 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 %
$ 692.00
$ 692.00 - $ 692.00
$ 692.00
$ 554.00
$ 554.00 - $ 554.00
$ 554.00

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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$ 692.00
$ 692.00 - $ 692.00
$ 692.00
$ 554.00
$ 554.00 - $ 554.00
$ 554.00
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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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$ 133.00
$ 133.00 - $ 133.00
$ 133.00
$ 106.00
$ 106.00 - $ 106.00
$ 106.00

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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$ 133.00
$ 133.00 - $ 133.00
$ 133.00
$ 106.00
$ 106.00 - $ 106.00
$ 106.00
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$ 478.00
$ 478.00 - $ 478.00
$ 478.00
$ 381.00
$ 381.00 - $ 381.00
$ 381.00

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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$ 478.00
$ 478.00 - $ 478.00
$ 478.00
$ 381.00
$ 381.00 - $ 381.00
$ 381.00
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$ 603.00
$ 603.00 - $ 603.00
$ 603.00
$ 482.00
$ 482.00 - $ 482.00
$ 482.00

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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$ 603.00
$ 603.00 - $ 603.00
$ 603.00
$ 482.00
$ 482.00 - $ 482.00
$ 482.00
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$ 216.00
$ 216.00 - $ 216.00
$ 216.00
$ 173.00
$ 173.00 - $ 173.00
$ 173.00

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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$ 216.00
$ 216.00 - $ 216.00
$ 216.00
$ 173.00
$ 173.00 - $ 173.00
$ 173.00
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Save 19% Save %
$ 141.00
$ 141.00 - $ 141.00
$ 141.00
$ 114.00
$ 114.00 - $ 114.00
$ 114.00

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
$ 114.00
$ 114.00 - $ 114.00
$ 114.00
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$ 510.00
$ 510.00 - $ 510.00
$ 510.00
$ 408.00
$ 408.00 - $ 408.00
$ 408.00

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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$ 510.00
$ 510.00 - $ 510.00
$ 510.00
$ 408.00
$ 408.00 - $ 408.00
$ 408.00
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$ 205.00
$ 205.00 - $ 205.00
$ 205.00
$ 165.00
$ 165.00 - $ 165.00
$ 165.00

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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$ 205.00
$ 205.00 - $ 205.00
$ 205.00
$ 165.00
$ 165.00 - $ 165.00
$ 165.00
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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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$ 519.00
$ 519.00 - $ 519.00
$ 519.00
$ 415.00
$ 415.00 - $ 415.00
$ 415.00

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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$ 519.00
$ 519.00 - $ 519.00
$ 519.00
$ 415.00
$ 415.00 - $ 415.00
$ 415.00
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$ 546.00
$ 546.00 - $ 546.00
$ 546.00
$ 436.00
$ 436.00 - $ 436.00
$ 436.00

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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$ 546.00
$ 546.00 - $ 546.00
$ 546.00
$ 436.00
$ 436.00 - $ 436.00
$ 436.00
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$ 535.00
$ 535.00 - $ 535.00
$ 535.00
$ 429.00
$ 429.00 - $ 429.00
$ 429.00

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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$ 535.00
$ 535.00 - $ 535.00
$ 535.00
$ 429.00
$ 429.00 - $ 429.00
$ 429.00
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$ 519.00
$ 519.00 - $ 519.00
$ 519.00
$ 415.00
$ 415.00 - $ 415.00
$ 415.00

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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$ 519.00
$ 519.00 - $ 519.00
$ 519.00
$ 415.00
$ 415.00 - $ 415.00
$ 415.00
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$ 474.00
$ 474.00 - $ 474.00
$ 474.00
$ 379.00
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$ 379.00

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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$ 474.00
$ 474.00 - $ 474.00
$ 474.00
$ 379.00
$ 379.00 - $ 379.00
$ 379.00
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$ 521.00
$ 521.00 - $ 521.00
$ 521.00
$ 417.00
$ 417.00 - $ 417.00
$ 417.00

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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$ 521.00
$ 521.00 - $ 521.00
$ 521.00
$ 417.00
$ 417.00 - $ 417.00
$ 417.00
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$ 610.00
$ 610.00 - $ 610.00
$ 610.00
$ 489.00
$ 489.00 - $ 489.00
$ 489.00

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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$ 610.00
$ 610.00 - $ 610.00
$ 610.00
$ 489.00
$ 489.00 - $ 489.00
$ 489.00
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$ 681.00
$ 681.00 - $ 681.00
$ 681.00
$ 544.00
$ 544.00 - $ 544.00
$ 544.00

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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$ 681.00
$ 681.00 - $ 681.00
$ 681.00
$ 544.00
$ 544.00 - $ 544.00
$ 544.00
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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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$ 387.00
$ 387.00 - $ 387.00
$ 387.00
$ 309.00
$ 309.00 - $ 309.00
$ 309.00

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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$ 387.00
$ 387.00 - $ 387.00
$ 387.00
$ 309.00
$ 309.00 - $ 309.00
$ 309.00
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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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$ 298.00
$ 298.00 - $ 298.00
$ 298.00
$ 239.00
$ 239.00 - $ 239.00
$ 239.00

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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$ 298.00
$ 298.00 - $ 298.00
$ 298.00
$ 239.00
$ 239.00 - $ 239.00
$ 239.00
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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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$ 273.00
$ 273.00 - $ 273.00
$ 273.00
$ 218.00
$ 218.00 - $ 218.00
$ 218.00

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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$ 273.00
$ 273.00 - $ 273.00
$ 273.00
$ 218.00
$ 218.00 - $ 218.00
$ 218.00
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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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$ 271.00
$ 271.00 - $ 271.00
$ 271.00
$ 216.00
$ 216.00 - $ 216.00
$ 216.00

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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$ 271.00
$ 271.00 - $ 271.00
$ 271.00
$ 216.00
$ 216.00 - $ 216.00
$ 216.00
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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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$ 300.00
$ 300.00 - $ 300.00
$ 300.00
$ 241.00
$ 241.00 - $ 241.00
$ 241.00

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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$ 300.00
$ 300.00 - $ 300.00
$ 300.00
$ 241.00
$ 241.00 - $ 241.00
$ 241.00
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