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4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare (LTBU3)
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare, view 2
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare, view 3
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare, view 4
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare, view 5
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare, view 6
4LifetimeLines brass brake line unions, 3/16" 3/8-24 inverted flare, 50 pack (LTBU3-50)
4LifetimeLines steel brake line union, 3/16" 3/8-24 bubble flare (LTBU7)
4LifetimeLines brass brake line union, 3/16" M10x1.0 inverted flare (LTBU9)
4LifetimeLines brass brake line unions, 3/16" M10x1.0 inverted flare, 50 pack (LTBU9-50)
4LifetimeLines steel brake line union, 3/16" M10x1.0 bubble flare (LTBU8)
4LifetimeLines brass brake line union, 1/4" 7/16-24 inverted flare (LTBU4)
4LifetimeLines brass brake line union, 5/16" 1/2-20 inverted flare (LTBU5)
4LifetimeLines brass brake line union, 3/8" 5/8-18 inverted flare (LTBU6)
4LifetimeLines brass brake line union, 6 mm M12x1.0 bubble flare (LTBU10)
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare (LTBU3)
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare, view 2
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare, view 3
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare, view 4
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare, view 5
4LifetimeLines brass brake line union, 3/16" 3/8-24 inverted flare, view 6
4LifetimeLines brass brake line unions, 3/16" 3/8-24 inverted flare, 50 pack (LTBU3-50)
4LifetimeLines steel brake line union, 3/16" 3/8-24 bubble flare (LTBU7)
4LifetimeLines brass brake line union, 3/16" M10x1.0 inverted flare (LTBU9)
4LifetimeLines brass brake line unions, 3/16" M10x1.0 inverted flare, 50 pack (LTBU9-50)
4LifetimeLines steel brake line union, 3/16" M10x1.0 bubble flare (LTBU8)
4LifetimeLines brass brake line union, 1/4" 7/16-24 inverted flare (LTBU4)
4LifetimeLines brass brake line union, 5/16" 1/2-20 inverted flare (LTBU5)
4LifetimeLines brass brake line union, 3/8" 5/8-18 inverted flare (LTBU6)
4LifetimeLines brass brake line union, 6 mm M12x1.0 bubble flare (LTBU10)

4LifetimeLines Brass & Steel Brake Line Unions, 3/16" to 3/8" & 6 mm, SAE & Metric

$12.00
4.9
Rated 4.9 out of 5 stars
12 Reviews

SKU: LTBU3

Size, thread and material
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Not sure what size you need? 3/16" is the most common brake line size — check the size chart or call 1 (855) 928-4024.

4LifetimeLines Brass & Steel Brake Line Unions join two lengths of brake line. Choose the line size, thread and flare type: 3/16", 1/4", 5/16", 3/8" or 6 mm line, SAE or metric threads, inverted (SAE double) or bubble (ISO) flare. The 3/8-24 and M10x1.0 bubble unions are steel; the rest are brass. Packs of 10, with 50-packs of the 3/16" 3/8-24 and M10x1.0 inverted brass unions.

What's in the box

  • Brake line unions in the size and pack you choose (10 or 50)

Sizes

Line size Thread Flare Material Pack SKU
3/16" 3/8-24 inverted brass 10 LTBU3
3/16" 3/8-24 inverted brass 50 LTBU3-50
3/16" 3/8-24 bubble steel 10 LTBU7
3/16" M10x1.0 inverted brass 10 LTBU9
3/16" M10x1.0 inverted brass 50 LTBU9-50
3/16" M10x1.0 bubble steel 10 LTBU8
1/4" 7/16-24 inverted brass 10 LTBU4
5/16" 1/2-20 inverted brass 10 LTBU5
3/8" 5/8-18 inverted brass 10 LTBU6
6 mm M12x1.0 bubble brass 10 LTBU10

How to use it

A union joins two lengths of brake line. Flare both line ends with the tube nuts on the line, thread one tube nut into each end of the union and tighten. Bleed the brakes and check the joint for leaks.

Brake safety note: Use only SAE double (inverted) or ISO bubble flares on hydraulic brake lines. Single flares are not safe for brake systems.

Questions

Which union do I need? Match the line size, the thread on your tube nuts and the flare type on the line ends.

Inverted or bubble? Inverted-flare unions take SAE double (inverted) flares; bubble unions take ISO bubble flares. Don't mix them.

Is there a stainless version? Yes. 4LifetimeLines sells stainless steel brake line unions separately.

Warranty and support

Covered by the 4Lifetime Limited Lifetime Warranty (see 4lifetimelines.com/pages/warranty). Questions? Email hello@4lifetimelines.com or call 1 (855) 928-4024, Monday–Friday, 9:00 AM–5:00 PM ET.

Type: Brake line union (joins two lines)
Material: Brass; steel for the 3/16" 3/8-24 and M10x1.0 bubble unions
Line sizes: 3/16", 1/4", 5/16", 3/8", 6 mm
Threads: 3/8-24, 7/16-24, 1/2-20, 5/8-18, M10x1.0, M12x1.0
Flare types: Inverted (SAE double) or bubble (ISO), by option
Pack: 10, or 50 (3/16" 3/8-24 and M10x1.0 inverted brass)
Vehicle fit: Universal (not vehicle-specific)
Warranty: 4Lifetime Limited Lifetime Warranty

Options and SKUs
3/16", 3/8-24 inverted, brass, 10 pack: LTBU3
3/16", 3/8-24 inverted, brass, 50 pack: LTBU3-50
3/16", 3/8-24 bubble, steel, 10 pack: LTBU7
3/16", M10x1.0 inverted, brass, 10 pack: LTBU9
3/16", M10x1.0 inverted, brass, 50 pack: LTBU9-50
3/16", M10x1.0 bubble, steel, 10 pack: LTBU8
1/4", 7/16-24 inverted, brass, 10 pack: LTBU4
5/16", 1/2-20 inverted, brass, 10 pack: LTBU5
3/8", 5/8-18 inverted, brass, 10 pack: LTBU6
6 mm, M12x1.0 bubble, brass, 10 pack: LTBU10

  • 4.8★ from nearly 4,000 Amazon ratings
  • Free US shipping on orders $50+
  • Ships same day when ordered by 2 PM ET (Mon–Fri)
  • Lifetime warranty on every product

Lifetime Quality, Covered — for Life

Zero Risk, Maximum Confidence

Built to Endure. Guaranteed to Perform.

One-Time Purchase. Lifetime Assurance.

Lifetime Quality, Covered — for Life

Zero Risk, Maximum Confidence

Built to Endure. Guaranteed to Perform.

One-Time Purchase. Lifetime Assurance.

Lifetime Quality, Covered — for Life

Zero Risk, Maximum Confidence

Built to Endure. Guaranteed to Perform.

One-Time Purchase. Lifetime Assurance.

Lifetime Quality, Covered — for Life

Zero Risk, Maximum Confidence

Built to Endure. Guaranteed to Perform.

One-Time Purchase. Lifetime Assurance.

Lifetime Quality, Covered — for Life

Zero Risk, Maximum Confidence

Built to Endure. Guaranteed to Perform.

One-Time Purchase. Lifetime Assurance.

Lifetime Quality, Covered — for Life

Zero Risk, Maximum Confidence

Built to Endure. Guaranteed to Perform.

One-Time Purchase. Lifetime Assurance.

Lifetime Quality, Covered — for Life

Zero Risk, Maximum Confidence

Built to Endure. Guaranteed to Perform.

One-Time Purchase. Lifetime Assurance.

4.9
Rated 4.9 out of 5 stars
Based on 12 reviews
100%would recommend this product
12 reviews
  • Rated 5 out of 5 stars
    1 year ago
    All products I bought from you.

    Very Nice!

    DC
    David C.
  • Rated 5 out of 5 stars
    1 year ago
    Quality

    I found out the hard way not to buy cheap knockoff brakeline kits from Amazon. I'm glad I found 4LifetimeLines! High quality brass unions and REAL copper nickel tubing. Will shop here from now on!

    NM
    Nathaniel M.
  • Rated 5 out of 5 stars
    2 years ago
    Nice

    Nice

    SW
    Stephen W.
  • Rated 5 out of 5 stars
    3 years ago
    Good deal

    Good quality

    GG
    George G.
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Ideal Products

Ideal stuff for fabricating brake lines brake lines at a very good price.Kit very well covers the materials for doing the whole brake line system.

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This was my first purchase and the experience has been fantastic. Great products, competitive prices, and fast shipping. Communication is also top notch.

Great products, competitive prices, and fast shipping.

This was my first purchase and the experience has been fantastic. Great products, competitive prices, and fast shipping. Communication is also top notch.