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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
€7,95 - €7,95
€7,95
€7,95 - €7,95
€7,95

Foster 81-4, 3/8" Industrial Plug x 1/2" Push-On Hose Stem, 4 Series, 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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€7,95 - €7,95
€7,95
€7,95 - €7,95
€7,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€19,95 - €19,95
€19,95
€19,95 - €19,95
€19,95

Foster 71-4B, 3/8" Industrial Plug x 3/8" Push-On Hose Stem, 4 Series, 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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€19,95 - €19,95
€19,95
€19,95 - €19,95
€19,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€4,95 - €4,95
€4,95
€4,95 - €4,95
€4,95

Foster 71-4, 3/8" Industrial Plug x 3/8" Push-On Hose Stem, 4 Series, 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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€4,95 - €4,95
€4,95
€4,95 - €4,95
€4,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€5,95 - €5,95
€5,95
€5,95 - €5,95
€5,95

Foster 51-4, 3/8" Industrial Plug x 1/4" Push-On Hose Stem, 4 Series, 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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€5,95 - €5,95
€5,95
€5,95 - €5,95
€5,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€5,95 - €5,95
€5,95
€5,95 - €5,95
€5,95

Foster 49-4, 3/8" Industrial Plug x 1/2" Hose ID, 4 Series, 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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€5,95 - €5,95
€5,95
€5,95 - €5,95
€5,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€7,95 - €7,95
€7,95
€7,95 - €7,95
€7,95

Foster 48-4B, 3/8" Industrial Plug x 3/8" Hose ID, 4 Series, 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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€7,95 - €7,95
€7,95
€7,95 - €7,95
€7,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€4,95 - €4,95
€4,95
€4,95 - €4,95
€4,95

Foster 48-4, 3/8" Industrial Plug x 3/8" Hose ID, 4 Series, 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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€4,95 - €4,95
€4,95
€4,95 - €4,95
€4,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€7,95 - €7,95
€7,95
€7,95 - €7,95
€7,95

Foster 47-4, 3/8" Industrial Plug x 5/16" Hose ID, 4 Series, 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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€7,95 - €7,95
€7,95
€7,95 - €7,95
€7,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€6,95 - €6,95
€6,95
€6,95 - €6,95
€6,95

Foster 46-4, 3/8" Industrial Plug x 1/4" Hose ID, 4 Series, Steel

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 46-4 is a Steel 3/8" industrial plug from the Foster 4 Series — a high-flo...

View full details
€6,95 - €6,95
€6,95
€6,95 - €6,95
€6,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€12,95 - €12,95
€12,95
€12,95 - €12,95
€12,95

Foster 44S-4, 3/8" Industrial Plug x 1/2" Male NPT, 4 Series, Free Swivel, Brass/Steel

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

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€12,95 - €12,95
€12,95
€12,95 - €12,95
€12,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€9,95 - €9,95
€9,95
€9,95 - €9,95
€9,95

Foster 42S-4, 3/8" Industrial Plug x 3/8" Male NPT, 4 Series, Free Swivel, Brass/Steel

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

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€9,95 - €9,95
€9,95
€9,95 - €9,95
€9,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€14,95 - €14,95
€14,95
€14,95 - €14,95
€14,95

Foster 40S-4, 3/8" Industrial Plug x 1/4" Male NPT, 4 Series, Free Swivel, Brass/Steel

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

View full details
€14,95 - €14,95
€14,95
€14,95 - €14,95
€14,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€5,95 - €5,95
€5,95
€5,95 - €5,95
€5,95

Foster 44-4, 3/8" Industrial Plug x 1/2" Male NPT, 4 Series, 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...

View full details
€5,95 - €5,95
€5,95
€5,95 - €5,95
€5,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€10,95 - €10,95
€10,95
€10,95 - €10,95
€10,95

Foster 42-4S/S, 3/8" Industrial Plug x 3/8" Male NPT, 4 Series, 303 Stainless

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 42-4S/S is a 303 Stainless 3/8" industrial plug from the Foster 4 Series —...

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€10,95 - €10,95
€10,95
€10,95 - €10,95
€10,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€6,95 - €6,95
€6,95
€6,95 - €6,95
€6,95

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

View full details
€6,95 - €6,95
€6,95
€6,95 - €6,95
€6,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€3,95 - €3,95
€3,95
€3,95 - €3,95
€3,95

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
€3,95 - €3,95
€3,95
€3,95 - €3,95
€3,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€7,95 - €7,95
€7,95
€7,95 - €7,95
€7,95

Foster 40-4S/S, 3/8" Industrial Plug x 1/4" Male NPT, 4 Series, 303 Stainless

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 40-4S/S is a 303 Stainless 3/8" industrial plug from the Foster 4 Series —...

View full details
€7,95 - €7,95
€7,95
€7,95 - €7,95
€7,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€6,95 - €6,95
€6,95
€6,95 - €6,95
€6,95

Foster 40-4B, 3/8" Industrial Plug x 1/4" Male NPT, 4 Series, 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
€6,95 - €6,95
€6,95
€6,95 - €6,95
€6,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€3,95 - €3,95
€3,95
€3,95 - €3,95
€3,95

Foster 40-4, 3/8" Industrial Plug x 1/4" Male NPT, 4 Series, 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...

View full details
€3,95 - €3,95
€3,95
€3,95 - €3,95
€3,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€8,95 - €8,95
€8,95
€8,95 - €8,95
€8,95

Foster 38-4, 3/8" Industrial Plug x 1/8" Male NPT, 4 Series, 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
€8,95 - €8,95
€8,95
€8,95 - €8,95
€8,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€6,95 - €6,95
€6,95
€6,95 - €6,95
€6,95

Foster 45-4, 3/8" Industrial Plug x 1/2" Female NPT, 4 Series, 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...

View full details
€6,95 - €6,95
€6,95
€6,95 - €6,95
€6,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€13,95 - €13,95
€13,95
€13,95 - €13,95
€13,95

Foster 43-4S/S, 3/8" Industrial Plug x 3/8" Female NPT, 4 Series, 303 Stainless

Reliable, leak-free 3/8" connections for air and fluid lines. The Foster 43-4S/S is a 303 Stainless 3/8" industrial plug from the Foster 4 Series —...

View full details
€13,95 - €13,95
€13,95
€13,95 - €13,95
€13,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€4,95 - €4,95
€4,95
€4,95 - €4,95
€4,95

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

View full details
€4,95 - €4,95
€4,95
€4,95 - €4,95
€4,95
Foster BLH1B, 1/8" ISO-B Hydraulic Coupler x 1/8" Female NPT, ISO-B Series, Ball Lock, Brass
€3,95 - €3,95
€3,95
€3,95 - €3,95
€3,95

Foster 41-4, 3/8" Industrial Plug x 1/4" Female NPT, 4 Series, 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...

View full details
€3,95 - €3,95
€3,95
€3,95 - €3,95
€3,95

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