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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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$ 103.00
$ 103.00 - $ 103.00
$ 103.00
$ 82.00
$ 82.00 - $ 82.00
$ 82.00

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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$ 103.00
$ 103.00 - $ 103.00
$ 103.00
$ 82.00
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$ 82.00
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$ 607.00
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$ 607.00
$ 486.00
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$ 486.00

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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$ 607.00
$ 607.00 - $ 607.00
$ 607.00
$ 486.00
$ 486.00 - $ 486.00
$ 486.00
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$ 127.00
$ 127.00 - $ 127.00
$ 127.00
$ 103.00
$ 103.00 - $ 103.00
$ 103.00

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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$ 127.00
$ 127.00 - $ 127.00
$ 127.00
$ 103.00
$ 103.00 - $ 103.00
$ 103.00
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$ 607.00
$ 607.00 - $ 607.00
$ 607.00
$ 486.00
$ 486.00 - $ 486.00
$ 486.00

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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$ 607.00
$ 607.00 - $ 607.00
$ 607.00
$ 486.00
$ 486.00 - $ 486.00
$ 486.00
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$ 171.00
$ 171.00 - $ 171.00
$ 171.00
$ 137.00
$ 137.00 - $ 137.00
$ 137.00

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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$ 171.00
$ 171.00 - $ 171.00
$ 171.00
$ 137.00
$ 137.00 - $ 137.00
$ 137.00
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$ 103.00
$ 103.00 - $ 103.00
$ 103.00
$ 82.00
$ 82.00 - $ 82.00
$ 82.00

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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$ 103.00
$ 103.00 - $ 103.00
$ 103.00
$ 82.00
$ 82.00 - $ 82.00
$ 82.00
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$ 444.00
$ 444.00 - $ 444.00
$ 444.00
$ 357.00
$ 357.00 - $ 357.00
$ 357.00

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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$ 444.00
$ 444.00 - $ 444.00
$ 444.00
$ 357.00
$ 357.00 - $ 357.00
$ 357.00
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$ 607.00
$ 607.00 - $ 607.00
$ 607.00
$ 486.00
$ 486.00 - $ 486.00
$ 486.00

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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$ 607.00
$ 607.00 - $ 607.00
$ 607.00
$ 486.00
$ 486.00 - $ 486.00
$ 486.00
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$ 603.00
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$ 603.00
$ 482.00
$ 482.00 - $ 482.00
$ 482.00

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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$ 603.00
$ 603.00 - $ 603.00
$ 603.00
$ 482.00
$ 482.00 - $ 482.00
$ 482.00
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$ 459.00
$ 459.00 - $ 459.00
$ 459.00
$ 368.00
$ 368.00 - $ 368.00
$ 368.00

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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$ 459.00
$ 459.00 - $ 459.00
$ 459.00
$ 368.00
$ 368.00 - $ 368.00
$ 368.00
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$ 622.00
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$ 622.00
$ 497.00
$ 497.00 - $ 497.00
$ 497.00

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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$ 622.00
$ 622.00 - $ 622.00
$ 622.00
$ 497.00
$ 497.00 - $ 497.00
$ 497.00
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$ 622.00
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$ 622.00
$ 497.00
$ 497.00 - $ 497.00
$ 497.00

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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$ 622.00
$ 622.00 - $ 622.00
$ 622.00
$ 497.00
$ 497.00 - $ 497.00
$ 497.00
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$ 133.00
$ 133.00 - $ 133.00
$ 133.00
$ 107.00
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$ 107.00

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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$ 133.00
$ 133.00 - $ 133.00
$ 133.00
$ 107.00
$ 107.00 - $ 107.00
$ 107.00
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$ 177.00
$ 177.00 - $ 177.00
$ 177.00
$ 141.00
$ 141.00 - $ 141.00
$ 141.00

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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$ 177.00
$ 177.00 - $ 177.00
$ 177.00
$ 141.00
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$ 141.00
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$ 188.00
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$ 188.00
$ 152.00
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$ 152.00

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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$ 188.00
$ 188.00 - $ 188.00
$ 188.00
$ 152.00
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$ 152.00
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$ 457.00
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$ 457.00
$ 366.00
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$ 366.00

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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$ 457.00
$ 457.00 - $ 457.00
$ 457.00
$ 366.00
$ 366.00 - $ 366.00
$ 366.00
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$ 603.00
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$ 603.00
$ 482.00
$ 482.00 - $ 482.00
$ 482.00

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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$ 603.00
$ 603.00 - $ 603.00
$ 603.00
$ 482.00
$ 482.00 - $ 482.00
$ 482.00
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$ 660.00
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$ 660.00
$ 530.00
$ 530.00 - $ 530.00
$ 530.00

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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$ 660.00
$ 660.00 - $ 660.00
$ 660.00
$ 530.00
$ 530.00 - $ 530.00
$ 530.00
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$ 175.00
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$ 175.00
$ 139.00
$ 139.00 - $ 139.00
$ 139.00

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...

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$ 175.00
$ 175.00 - $ 175.00
$ 175.00
$ 139.00
$ 139.00 - $ 139.00
$ 139.00
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$ 615.00
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$ 615.00
$ 492.00
$ 492.00 - $ 492.00
$ 492.00

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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$ 615.00
$ 615.00 - $ 615.00
$ 615.00
$ 492.00
$ 492.00 - $ 492.00
$ 492.00
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$ 531.00
$ 531.00 - $ 531.00
$ 531.00
$ 425.00
$ 425.00 - $ 425.00
$ 425.00

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...

View full details
$ 531.00
$ 531.00 - $ 531.00
$ 531.00
$ 425.00
$ 425.00 - $ 425.00
$ 425.00
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$ 531.00
$ 531.00 - $ 531.00
$ 531.00
$ 425.00
$ 425.00 - $ 425.00
$ 425.00

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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$ 531.00
$ 531.00 - $ 531.00
$ 531.00
$ 425.00
$ 425.00 - $ 425.00
$ 425.00
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$ 120.00
$ 120.00 - $ 120.00
$ 120.00
$ 95.00
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$ 95.00

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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$ 120.00
$ 120.00 - $ 120.00
$ 120.00
$ 95.00
$ 95.00 - $ 95.00
$ 95.00
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$ 630.00
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$ 630.00
$ 505.00
$ 505.00 - $ 505.00
$ 505.00

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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$ 630.00
$ 630.00 - $ 630.00
$ 630.00
$ 505.00
$ 505.00 - $ 505.00
$ 505.00
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