Skip to content

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.

Filters

Save 20% Save %
$ 179.00
$ 179.00 - $ 179.00
$ 179.00
$ 143.00
$ 143.00 - $ 143.00
$ 143.00

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...

View full details
$ 179.00
$ 179.00 - $ 179.00
$ 179.00
$ 143.00
$ 143.00 - $ 143.00
$ 143.00
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 %
$ 86.00
$ 86.00 - $ 86.00
$ 86.00
$ 69.00
$ 69.00 - $ 69.00
$ 69.00

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...

View full details
$ 86.00
$ 86.00 - $ 86.00
$ 86.00
$ 69.00
$ 69.00 - $ 69.00
$ 69.00
Save 20% Save %
Save 21% Save %
$ 111.00
$ 111.00 - $ 111.00
$ 111.00
$ 88.00
$ 88.00 - $ 88.00
$ 88.00

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...

View full details
$ 111.00
$ 111.00 - $ 111.00
$ 111.00
$ 88.00
$ 88.00 - $ 88.00
$ 88.00
Save 21% Save %
Save 20% Save %
$ 121.00
$ 121.00 - $ 121.00
$ 121.00
$ 97.00
$ 97.00 - $ 97.00
$ 97.00

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...

View full details
$ 121.00
$ 121.00 - $ 121.00
$ 121.00
$ 97.00
$ 97.00 - $ 97.00
$ 97.00
Save 20% Save %
Save 20% Save %
$ 434.00
$ 434.00 - $ 434.00
$ 434.00
$ 346.00
$ 346.00 - $ 346.00
$ 346.00

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...

View full details
$ 434.00
$ 434.00 - $ 434.00
$ 434.00
$ 346.00
$ 346.00 - $ 346.00
$ 346.00
Save 20% Save %
Save 20% Save %
$ 548.00
$ 548.00 - $ 548.00
$ 548.00
$ 438.00
$ 438.00 - $ 438.00
$ 438.00

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...

View full details
$ 548.00
$ 548.00 - $ 548.00
$ 548.00
$ 438.00
$ 438.00 - $ 438.00
$ 438.00
Save 20% Save %
Save 20% Save %
$ 197.00
$ 197.00 - $ 197.00
$ 197.00
$ 157.00
$ 157.00 - $ 157.00
$ 157.00

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...

View full details
$ 197.00
$ 197.00 - $ 197.00
$ 197.00
$ 157.00
$ 157.00 - $ 157.00
$ 157.00
Save 20% Save %
Save 19% Save %
$ 128.00
$ 128.00 - $ 128.00
$ 128.00
$ 104.00
$ 104.00 - $ 104.00
$ 104.00

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...

View full details
$ 128.00
$ 128.00 - $ 128.00
$ 128.00
$ 104.00
$ 104.00 - $ 104.00
$ 104.00
Save 19% Save %
Save 20% Save %
$ 464.00
$ 464.00 - $ 464.00
$ 464.00
$ 371.00
$ 371.00 - $ 371.00
$ 371.00

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...

View full details
$ 464.00
$ 464.00 - $ 464.00
$ 464.00
$ 371.00
$ 371.00 - $ 371.00
$ 371.00
Save 20% Save %
Save 19% Save %
$ 186.00
$ 186.00 - $ 186.00
$ 186.00
$ 150.00
$ 150.00 - $ 150.00
$ 150.00

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...

View full details
$ 186.00
$ 186.00 - $ 186.00
$ 186.00
$ 150.00
$ 150.00 - $ 150.00
$ 150.00
Save 19% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
Save 20% Save %
$ 472.00
$ 472.00 - $ 472.00
$ 472.00
$ 377.00
$ 377.00 - $ 377.00
$ 377.00

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...

View full details
$ 472.00
$ 472.00 - $ 472.00
$ 472.00
$ 377.00
$ 377.00 - $ 377.00
$ 377.00
Save 20% Save %
Save 20% Save %
$ 496.00
$ 496.00 - $ 496.00
$ 496.00
$ 396.00
$ 396.00 - $ 396.00
$ 396.00

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...

View full details
$ 496.00
$ 496.00 - $ 496.00
$ 496.00
$ 396.00
$ 396.00 - $ 396.00
$ 396.00
Save 20% Save %
Save 20% Save %
$ 486.00
$ 486.00 - $ 486.00
$ 486.00
$ 390.00
$ 390.00 - $ 390.00
$ 390.00

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...

View full details
$ 486.00
$ 486.00 - $ 486.00
$ 486.00
$ 390.00
$ 390.00 - $ 390.00
$ 390.00
Save 20% Save %
Save 20% Save %
$ 472.00
$ 472.00 - $ 472.00
$ 472.00
$ 377.00
$ 377.00 - $ 377.00
$ 377.00

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...

View full details
$ 472.00
$ 472.00 - $ 472.00
$ 472.00
$ 377.00
$ 377.00 - $ 377.00
$ 377.00
Save 20% Save %
Save 20% Save %
$ 431.00
$ 431.00 - $ 431.00
$ 431.00
$ 345.00
$ 345.00 - $ 345.00
$ 345.00

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...

View full details
$ 431.00
$ 431.00 - $ 431.00
$ 431.00
$ 345.00
$ 345.00 - $ 345.00
$ 345.00
Save 20% Save %
Save 20% Save %
$ 474.00
$ 474.00 - $ 474.00
$ 474.00
$ 379.00
$ 379.00 - $ 379.00
$ 379.00

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...

View full details
$ 474.00
$ 474.00 - $ 474.00
$ 474.00
$ 379.00
$ 379.00 - $ 379.00
$ 379.00
Save 20% Save %
Save 20% Save %
$ 555.00
$ 555.00 - $ 555.00
$ 555.00
$ 445.00
$ 445.00 - $ 445.00
$ 445.00

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...

View full details
$ 555.00
$ 555.00 - $ 555.00
$ 555.00
$ 445.00
$ 445.00 - $ 445.00
$ 445.00
Save 20% Save %
Save 20% Save %
$ 619.00
$ 619.00 - $ 619.00
$ 619.00
$ 495.00
$ 495.00 - $ 495.00
$ 495.00

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...

View full details
$ 619.00
$ 619.00 - $ 619.00
$ 619.00
$ 495.00
$ 495.00 - $ 495.00
$ 495.00
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 %
$ 352.00
$ 352.00 - $ 352.00
$ 352.00
$ 281.00
$ 281.00 - $ 281.00
$ 281.00

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...

View full details
$ 352.00
$ 352.00 - $ 352.00
$ 352.00
$ 281.00
$ 281.00 - $ 281.00
$ 281.00
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 %
$ 271.00
$ 271.00 - $ 271.00
$ 271.00
$ 217.00
$ 217.00 - $ 217.00
$ 217.00

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...

View full details
$ 271.00
$ 271.00 - $ 271.00
$ 271.00
$ 217.00
$ 217.00 - $ 217.00
$ 217.00
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 %
$ 248.00
$ 248.00 - $ 248.00
$ 248.00
$ 198.00
$ 198.00 - $ 198.00
$ 198.00

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...

View full details
$ 248.00
$ 248.00 - $ 248.00
$ 248.00
$ 198.00
$ 198.00 - $ 198.00
$ 198.00
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 %
$ 247.00
$ 247.00 - $ 247.00
$ 247.00
$ 197.00
$ 197.00 - $ 197.00
$ 197.00

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...

View full details
$ 247.00
$ 247.00 - $ 247.00
$ 247.00
$ 197.00
$ 197.00 - $ 197.00
$ 197.00
Save 20% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
Save 19% Save %
$ 272.00
$ 272.00 - $ 272.00
$ 272.00
$ 219.00
$ 219.00 - $ 219.00
$ 219.00

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...

View full details
$ 272.00
$ 272.00 - $ 272.00
$ 272.00
$ 219.00
$ 219.00 - $ 219.00
$ 219.00
Save 19% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
Save 20% Save %
$ 240.00
$ 240.00 - $ 240.00
$ 240.00
$ 191.00
$ 191.00 - $ 191.00
$ 191.00

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...

View full details
$ 240.00
$ 240.00 - $ 240.00
$ 240.00
$ 191.00
$ 191.00 - $ 191.00
$ 191.00
Save 20% Save %

Request a Quote

Bulk and dealer pricing. Tell us what you need and we’ll reply within one business day.