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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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$ 93.00
$ 93.00 - $ 93.00
$ 93.00
$ 74.00
$ 74.00 - $ 74.00
$ 74.00

Foster 40-4, 4 Series, Industrial Plug, 1/4" Male NPT, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 40-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 93.00
$ 93.00 - $ 93.00
$ 93.00
$ 74.00
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$ 74.00
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$ 551.00
$ 551.00 - $ 551.00
$ 551.00
$ 441.00
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$ 441.00

Foster FM4204, 4 Series, Industrial Coupler, Automatic, 3/8" Female NPT, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4204 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 551.00
$ 551.00 - $ 551.00
$ 551.00
$ 441.00
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$ 441.00
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$ 116.00
$ 116.00 - $ 116.00
$ 116.00
$ 93.00
$ 93.00 - $ 93.00
$ 93.00

Foster 43-4, 4 Series, Industrial Plug, 3/8" Female NPT, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 43-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 116.00
$ 116.00 - $ 116.00
$ 116.00
$ 93.00
$ 93.00 - $ 93.00
$ 93.00
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$ 551.00
$ 551.00 - $ 551.00
$ 551.00
$ 441.00
$ 441.00 - $ 441.00
$ 441.00

Foster FM4303, 4 Series, Industrial Coupler, Automatic, 3/8" Male NPT, 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...

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$ 551.00
$ 551.00 - $ 551.00
$ 551.00
$ 441.00
$ 441.00 - $ 441.00
$ 441.00
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$ 155.00
$ 155.00 - $ 155.00
$ 155.00
$ 124.00
$ 124.00 - $ 124.00
$ 124.00

Foster 42-4B, 4 Series, Industrial Plug, 3/8" Male NPT, Brass

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

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$ 155.00
$ 155.00 - $ 155.00
$ 155.00
$ 124.00
$ 124.00 - $ 124.00
$ 124.00
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$ 93.00
$ 93.00 - $ 93.00
$ 93.00
$ 74.00
$ 74.00 - $ 74.00
$ 74.00

Foster 41-4, 4 Series, Industrial Plug, 1/4" Female NPT, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 41-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 93.00
$ 93.00 - $ 93.00
$ 93.00
$ 74.00
$ 74.00 - $ 74.00
$ 74.00
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$ 551.00
$ 551.00 - $ 551.00
$ 551.00
$ 441.00
$ 441.00 - $ 441.00
$ 441.00

Foster FM4304, 4 Series, Industrial Coupler, Automatic, 3/8" Male NPT, 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...

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$ 551.00
$ 551.00 - $ 551.00
$ 551.00
$ 441.00
$ 441.00 - $ 441.00
$ 441.00
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$ 403.00
$ 403.00 - $ 403.00
$ 403.00
$ 324.00
$ 324.00 - $ 324.00
$ 324.00

Foster 4004, 4 Series, Industrial Coupler, Manual, 1/4" Female NPT, 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...

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$ 403.00
$ 403.00 - $ 403.00
$ 403.00
$ 324.00
$ 324.00 - $ 324.00
$ 324.00
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$ 548.00
$ 548.00 - $ 548.00
$ 548.00
$ 438.00
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$ 438.00

Foster FM4004, 4 Series, Industrial Coupler, Automatic, 1/4" Female NPT, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4004 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 548.00
$ 548.00 - $ 548.00
$ 548.00
$ 438.00
$ 438.00 - $ 438.00
$ 438.00
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$ 417.00
$ 417.00 - $ 417.00
$ 417.00
$ 334.00
$ 334.00 - $ 334.00
$ 334.00

Foster 4204, 4 Series, Industrial Coupler, Manual, 3/8" Female NPT, 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...

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$ 417.00
$ 417.00 - $ 417.00
$ 417.00
$ 334.00
$ 334.00 - $ 334.00
$ 334.00
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$ 565.00
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$ 565.00
$ 452.00
$ 452.00 - $ 452.00
$ 452.00

Foster FM4404, 4 Series, Industrial Coupler, Automatic, 1/2" Female NPT, 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...

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$ 565.00
$ 565.00 - $ 565.00
$ 565.00
$ 452.00
$ 452.00 - $ 452.00
$ 452.00
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$ 121.00
$ 121.00 - $ 121.00
$ 121.00
$ 97.00
$ 97.00 - $ 97.00
$ 97.00

Foster 44-4, 4 Series, Industrial Plug, 1/2" Male NPT, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 44-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 121.00
$ 121.00 - $ 121.00
$ 121.00
$ 97.00
$ 97.00 - $ 97.00
$ 97.00
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$ 160.00
$ 160.00 - $ 160.00
$ 160.00
$ 128.00
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$ 128.00

Foster 45-4, 4 Series, Industrial Plug, 1/2" Female NPT, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 45-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 160.00
$ 160.00 - $ 160.00
$ 160.00
$ 128.00
$ 128.00 - $ 128.00
$ 128.00
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$ 565.00
$ 565.00 - $ 565.00
$ 565.00
$ 452.00
$ 452.00 - $ 452.00
$ 452.00

Foster FM4804, 4 Series, Industrial Coupler, Automatic, 3/8" Hose Barb, 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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$ 565.00
$ 565.00 - $ 565.00
$ 565.00
$ 452.00
$ 452.00 - $ 452.00
$ 452.00
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$ 171.00
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$ 171.00
$ 138.00
$ 138.00 - $ 138.00
$ 138.00

Foster 48-4B, 4 Series, Industrial Plug, 3/8" Hose Barb, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 48-4B is a Brass 3/8" industrial plug from the Foster 4 Series — a high-fl...

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$ 171.00
$ 171.00 - $ 171.00
$ 171.00
$ 138.00
$ 138.00 - $ 138.00
$ 138.00
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$ 415.00
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$ 415.00
$ 333.00
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$ 333.00

Foster 4104, 4 Series, Industrial Coupler, Manual, 1/4" Male NPT, Brass, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4104 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 415.00
$ 415.00 - $ 415.00
$ 415.00
$ 333.00
$ 333.00 - $ 333.00
$ 333.00
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$ 548.00
$ 548.00 - $ 548.00
$ 548.00
$ 438.00
$ 438.00 - $ 438.00
$ 438.00

Foster FM4104, 4 Series, Industrial Coupler, Automatic, 1/4" Male NPT, 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...

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$ 548.00
$ 548.00 - $ 548.00
$ 548.00
$ 438.00
$ 438.00 - $ 438.00
$ 438.00
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$ 600.00
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$ 600.00
$ 481.00
$ 481.00 - $ 481.00
$ 481.00

Foster FM1714, 4 Series, Industrial Coupler, Automatic, 3/8" Push-On Hose Barb, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM1714 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 600.00
$ 600.00 - $ 600.00
$ 600.00
$ 481.00
$ 481.00 - $ 481.00
$ 481.00
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$ 159.00
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$ 159.00
$ 126.00
$ 126.00 - $ 126.00
$ 126.00

Foster 40-4B, 4 Series, Industrial Plug, 1/4" Male NPT, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 40-4B is a Brass 3/8" industrial plug from the Foster 4 Series — a high-fl...

View full details
$ 159.00
$ 159.00 - $ 159.00
$ 159.00
$ 126.00
$ 126.00 - $ 126.00
$ 126.00
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$ 558.00
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$ 558.00
$ 446.00
$ 446.00 - $ 446.00
$ 446.00

Foster FM4504, 4 Series, Industrial Coupler, Automatic, 1/2" Male NPT, 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...

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$ 558.00
$ 558.00 - $ 558.00
$ 558.00
$ 446.00
$ 446.00 - $ 446.00
$ 446.00
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$ 483.00
$ 483.00 - $ 483.00
$ 483.00
$ 386.00
$ 386.00 - $ 386.00
$ 386.00

Foster 4404, 4 Series, Industrial Coupler, Manual, 1/2" Female NPT, 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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$ 483.00
$ 483.00 - $ 483.00
$ 483.00
$ 386.00
$ 386.00 - $ 386.00
$ 386.00
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$ 483.00
$ 483.00 - $ 483.00
$ 483.00
$ 386.00
$ 386.00 - $ 386.00
$ 386.00

Foster 4504, 4 Series, Industrial Coupler, Manual, 1/2" Male NPT, Brass, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 4504 is a Brass/Steel 3/8" industrial coupler from the Foster 4 Series — a...

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$ 483.00
$ 483.00 - $ 483.00
$ 483.00
$ 386.00
$ 386.00 - $ 386.00
$ 386.00
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$ 109.00
$ 109.00 - $ 109.00
$ 109.00
$ 86.00
$ 86.00 - $ 86.00
$ 86.00

Foster 48-4, 4 Series, Industrial Plug, 3/8" Hose Barb, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 48-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

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$ 109.00
$ 109.00 - $ 109.00
$ 109.00
$ 86.00
$ 86.00 - $ 86.00
$ 86.00
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$ 572.00
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$ 572.00
$ 458.00
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$ 458.00

Foster FM4904, 4 Series, Industrial Coupler, Automatic, 1/2" Hose Barb, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4904 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 572.00
$ 572.00 - $ 572.00
$ 572.00
$ 458.00
$ 458.00 - $ 458.00
$ 458.00
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