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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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Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass Save 20% Save %
$ 761.00
$ 761.00 - $ 761.00
$ 761.00
$ 610.00
$ 610.00 - $ 610.00
$ 610.00

Foster SLSD13-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 13/16" OD, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SLSD13-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 761.00
$ 761.00 - $ 761.00
$ 761.00
$ 610.00
$ 610.00 - $ 610.00
$ 610.00
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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 %
$ 667.00
$ 667.00 - $ 667.00
$ 667.00
$ 534.00
$ 534.00 - $ 534.00
$ 534.00

Foster FMSD13-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 13/16" OD, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FMSD13-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 667.00
$ 667.00 - $ 667.00
$ 667.00
$ 534.00
$ 534.00 - $ 534.00
$ 534.00
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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 %
$ 755.00
$ 755.00 - $ 755.00
$ 755.00
$ 605.00
$ 605.00 - $ 605.00
$ 605.00

Foster SLSD11-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 3/4" OD, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SLSD11-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 755.00
$ 755.00 - $ 755.00
$ 755.00
$ 605.00
$ 605.00 - $ 605.00
$ 605.00
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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 %
$ 656.00
$ 656.00 - $ 656.00
$ 656.00
$ 526.00
$ 526.00 - $ 526.00
$ 526.00

Foster FMSD11-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 3/4" OD, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FMSD11-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a h...

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$ 656.00
$ 656.00 - $ 656.00
$ 656.00
$ 526.00
$ 526.00 - $ 526.00
$ 526.00
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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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$ 744.00
$ 744.00 - $ 744.00
$ 744.00
$ 594.00
$ 594.00 - $ 594.00
$ 594.00

Foster SLSD9-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 11/16" OD, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SLSD9-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 744.00
$ 744.00 - $ 744.00
$ 744.00
$ 594.00
$ 594.00 - $ 594.00
$ 594.00
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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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$ 646.00
$ 646.00 - $ 646.00
$ 646.00
$ 517.00
$ 517.00 - $ 517.00
$ 517.00

Foster FMSD9-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 11/16" OD, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FMSD9-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 646.00
$ 646.00 - $ 646.00
$ 646.00
$ 517.00
$ 517.00 - $ 517.00
$ 517.00
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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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$ 732.00
$ 732.00 - $ 732.00
$ 732.00
$ 586.00
$ 586.00 - $ 586.00
$ 586.00

Foster SLSD7-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 5/8" OD, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SLSD7-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 732.00
$ 732.00 - $ 732.00
$ 732.00
$ 586.00
$ 586.00 - $ 586.00
$ 586.00
Save 20% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 868.00
$ 868.00 - $ 868.00
$ 868.00
$ 694.00
$ 694.00 - $ 694.00
$ 694.00

Foster FMSD7-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 3/8" ID x 5/8" OD, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FMSD7-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 868.00
$ 868.00 - $ 868.00
$ 868.00
$ 694.00
$ 694.00 - $ 694.00
$ 694.00
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 %
$ 732.00
$ 732.00 - $ 732.00
$ 732.00
$ 586.00
$ 586.00 - $ 586.00
$ 586.00

Foster SLSB7-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 1/4" ID x 5/8" OD, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SLSB7-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 732.00
$ 732.00 - $ 732.00
$ 732.00
$ 586.00
$ 586.00 - $ 586.00
$ 586.00
Save 20% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 660.00
$ 660.00 - $ 660.00
$ 660.00
$ 527.00
$ 527.00 - $ 527.00
$ 527.00

Foster FMSB7-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 1/4" ID x 5/8" OD, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FMSB7-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 660.00
$ 660.00 - $ 660.00
$ 660.00
$ 527.00
$ 527.00 - $ 527.00
$ 527.00
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 %
$ 725.00
$ 725.00 - $ 725.00
$ 725.00
$ 581.00
$ 581.00 - $ 581.00
$ 581.00

Foster SLSB5-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 1/4" ID x 9/16" OD, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SLSB5-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 725.00
$ 725.00 - $ 725.00
$ 725.00
$ 581.00
$ 581.00 - $ 581.00
$ 581.00
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 %
$ 653.00
$ 653.00 - $ 653.00
$ 653.00
$ 522.00
$ 522.00 - $ 522.00
$ 522.00

Foster FMSB5-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 1/4" ID x 9/16" OD, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FMSB5-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 653.00
$ 653.00 - $ 653.00
$ 653.00
$ 522.00
$ 522.00 - $ 522.00
$ 522.00
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 %
$ 682.00
$ 682.00 - $ 682.00
$ 682.00
$ 546.00
$ 546.00 - $ 546.00
$ 546.00

Foster SLSB3-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 1/4" ID x 1/2" OD, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SLSB3-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 682.00
$ 682.00 - $ 682.00
$ 682.00
$ 546.00
$ 546.00 - $ 546.00
$ 546.00
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 %
$ 613.00
$ 613.00 - $ 613.00
$ 613.00
$ 491.00
$ 491.00 - $ 491.00
$ 491.00

Foster FMSB3-4, 3/8" Industrial Coupler x Reusable Hose Fitting, 1/4" ID x 1/2" OD, 4 Series, Automatic, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FMSB3-4 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 613.00
$ 613.00 - $ 613.00
$ 613.00
$ 491.00
$ 491.00 - $ 491.00
$ 491.00
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 %
$ 687.00
$ 687.00 - $ 687.00
$ 687.00
$ 551.00
$ 551.00 - $ 551.00
$ 551.00

Foster FM1814W, 3/8" Industrial Coupler x 1/2" Push-On Hose Stem, 4 Series, Automatic, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM1814W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a...

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$ 687.00
$ 687.00 - $ 687.00
$ 687.00
$ 551.00
$ 551.00 - $ 551.00
$ 551.00
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 %
$ 718.00
$ 718.00 - $ 718.00
$ 718.00
$ 576.00
$ 576.00 - $ 576.00
$ 576.00

Foster SL1814, 3/8" Industrial Coupler x 1/2" Push-On Hose Stem, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL1814 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 718.00
$ 718.00 - $ 718.00
$ 718.00
$ 576.00
$ 576.00 - $ 576.00
$ 576.00
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 %
$ 619.00
$ 619.00 - $ 619.00
$ 619.00
$ 495.00
$ 495.00 - $ 495.00
$ 495.00

Foster FM1814, 3/8" Industrial Coupler x 1/2" Push-On Hose Stem, 4 Series, Automatic, 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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$ 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 %
$ 701.00
$ 701.00 - $ 701.00
$ 701.00
$ 560.00
$ 560.00 - $ 560.00
$ 560.00

Foster SL1714, 3/8" Industrial Coupler x 3/8" Push-On Hose Stem, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL1714 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 701.00
$ 701.00 - $ 701.00
$ 701.00
$ 560.00
$ 560.00 - $ 560.00
$ 560.00
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 %
$ 600.00
$ 600.00 - $ 600.00
$ 600.00
$ 481.00
$ 481.00 - $ 481.00
$ 481.00

Foster FM1714, 3/8" Industrial Coupler x 3/8" Push-On Hose Stem, 4 Series, Automatic, 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
Save 20% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 665.00
$ 665.00 - $ 665.00
$ 665.00
$ 531.00
$ 531.00 - $ 531.00
$ 531.00

Foster FM4904W, 3/8" Industrial Coupler x 1/2" Hose ID, 4 Series, Automatic, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4904W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a...

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$ 665.00
$ 665.00 - $ 665.00
$ 665.00
$ 531.00
$ 531.00 - $ 531.00
$ 531.00
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 %
$ 667.00
$ 667.00 - $ 667.00
$ 667.00
$ 534.00
$ 534.00 - $ 534.00
$ 534.00

Foster SL4904, 3/8" Industrial Coupler x 1/2" Hose ID, 4 Series, Automatic Sleeve Lock, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster SL4904 is a Brass 3/8" industrial coupler from the Foster 4 Series — a hig...

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$ 667.00
$ 667.00 - $ 667.00
$ 667.00
$ 534.00
$ 534.00 - $ 534.00
$ 534.00
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 %
$ 572.00
$ 572.00 - $ 572.00
$ 572.00
$ 458.00
$ 458.00 - $ 458.00
$ 458.00

Foster FM4904, 3/8" Industrial Coupler x 1/2" Hose ID, 4 Series, Automatic, 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
Save 20% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 632.00
$ 632.00 - $ 632.00
$ 632.00
$ 505.00
$ 505.00 - $ 505.00
$ 505.00

Foster FM4804W, 3/8" Industrial Coupler x 3/8" Hose ID, 4 Series, Automatic, Water, Brass/SS

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4804W is a Brass/SS 3/8" industrial coupler from the Foster 4 Series — a...

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$ 632.00
$ 632.00 - $ 632.00
$ 632.00
$ 505.00
$ 505.00 - $ 505.00
$ 505.00
Save 20% Save %
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
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$ 596.00
$ 596.00 - $ 596.00
$ 596.00
$ 477.00
$ 477.00 - $ 477.00
$ 477.00

Foster FM4804H, 3/8" Industrial Coupler x 3/8" Hose ID, 4 Series, Automatic, Heat/Viton, Brass

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster FM4804H is a Brass 3/8" industrial coupler from the Foster 4 Series — a hi...

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$ 596.00
$ 596.00 - $ 596.00
$ 596.00
$ 477.00
$ 477.00 - $ 477.00
$ 477.00
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