Brake line flaring tools, and the three end shapes one of which fits your car
The short answer
Prices in GBPUSDEUReach row carries the day it was read
A brake line is a steel pipe with a shaped end. There is no washer and no sealant: the shape you form on the end of the pipe is pressed into a cone in the fitting, and that contact is the seal. Which means the tool that forms the shape is the whole job, and the shape it forms has to be the one your car expects.
Before the rest of this page: brakes are the one system where a joint that is nearly right is worse than no joint at all, because it holds until the pedal is pushed hard. If you are not confident about bleeding the system and pressure testing what you have made, this is a job for a garage. Nothing below changes that.
The three shapes
Single flare. The pipe end is opened out into one cone. It is used on fuel and on low pressure lines, and it is not a brake joint: the single thickness of steel splits under braking pressure and vibration. Three titles here say single, always alongside something else.
Double flare, sometimes SAE 45 degrees. The end is folded back on itself and then coned, so the sealing face is two thicknesses of steel. This is what most cars use, and it is what four of these twelve titles name.
Bubble flare, also called DIN or ISO. The end is formed into a rounded bulge rather than a cone. Much of the European market uses it, and two titles here say the word. A double flare tool will not make one.
The three are not interchangeable and you cannot tell them apart by the fitting alone. Look at the end of the pipe you are taking off.
3/16in and 4.75mm are the same pipe
Five titles here say 3/16in. One says 4.75mm. Those are the same size, in the two systems the industry uses side by side, and that size is what almost every car and motorcycle brake line is made in.
One flaring kit goes wider, listing 1/4in, 5/16in and 3/8in as well, and the bender here is sized in the same three. Those sizes exist on fuel, transmission and some heavy vehicles. For a car brake job, the number to check is 3/16, however the listing spells it.
45 degrees, and the 37 that keeps appearing
Three titles state 45 degrees, which is the SAE angle the double flare uses. Two state 45/37, and the 37 is the AN angle, from aviation and hydraulics, used on braided lines and fittings rather than on the steel pipe under a car.
A kit that does both is not confused. It is a kit that covers a workshop rather than one car, and both titles here that mention 37 state 45 beside it, which is the right way round. A tool offering only 37 degrees would not be a brake tool at all, and there is none on this page.
Handheld, turret, or bench
The cheap tools here are a clamp bar and a screw: the pipe is held in a split die and a cone is driven into it. They work, they are slow, and they slip if the die is not tight or the pipe is hard.
The dearer ones use a turret, a rotating head carrying the dies so the right one is always in line, which is faster and much more repeatable. Two titles count their pieces, five and eight, and three arrive in a case.
For one repair, the handheld tool is fine and you will swear at it. For a restoration, or a whole car’s lines, the turret pays for itself in ruined pipes not made.
Copper-nickel, and why it matters here
Nothing on this page states what material it is rated to flare, and it is the question that decides whether a cheap tool works.
Copper-nickel line, sold as Kunifer or Cupro-Nickel, is soft enough to flare by hand, does not rust, and is legal for brake lines in the UK. Plain steel line is harder, rusts, and fights every cheap tool on this page.
If you are buying a flaring tool for a car you own, buy copper-nickel line to go with it. It is the single change that makes this job achievable at home.
What else you need
One listing here bundles the consumables: 25ft of 3/16in pipe, sixteen fittings and four unions, with a flaring tool. That is close to a whole line’s worth of parts, and buying fittings separately in the right thread is the fiddliest part of the job.
One listing is a bender, in 6, 8 and 10mm. It is not optional in practice. A brake line has to follow the car, and a pipe bent by hand round a tight radius kinks; a kinked pipe is scrap, and you find out after you have flared both ends.
What I would actually do
If you are doing a car properly, the kit whose title names single, bubble and double at 45 and 37. Two listings here name every shape you might meet under a car older than you expected, and this is the one that does it without buying a workshop’s worth of dies.
If you already know the car takes a 3/16in double flare, the handheld double flaring tool. It does that one job, and that one job is most of them.
Buy the bender at the same time, whichever tool you choose.
And if you are replacing a whole run rather than a section, the line kit with the fittings and unions, so the parts arrive together in the right size.
Then test it properly before the car goes back on the road.
Side by side
Prices in GBPUSDEUR. Each row carries the date its price was read.
| Product | Price | Why it is here | Where to buyLink |
|---|---|---|---|
| Best overall Car Brake Tube Line Flare Pipe Flaring Tool 45/37 | £75.96$98.35€89.38checked 18 Oct 2026 | Names all three flare shapes in its title, single, bubble and double, at both 45 and 37 degrees, which is every shape a car is likely to want | Check opens in a new tab |
| If you only need the common job 3/16in Double Flaring Tool Metal Handheld Brake Line | £13.58$17.58€15.98checked 18 Oct 2026 | A handheld double flaring tool in 3/16in, which is the size and the shape most car and motorcycle brake lines actually use | Check opens in a new tab |
| The other half of the job LIBRATON Tube Bender, Pipe 3-IN-1, 1/4"(6mm) | £11.84$15.79€13.93checked 18 Oct 2026 | A three in one bender for 6, 8 and 10mm. Flaring an end is useless if the pipe kinks on the way to it, and a kinked pipe is scrap | Check opens in a new tab |
What the title has to tell you
- Which flares it makes. Four titles say double, three say single, two say bubble. A tool that only makes a single flare cannot make a brake line, whatever else the listing says about brakes.
- 3/16in, which is 4.75mm. Five titles use the imperial name and one uses the metric, and they are the same pipe: the size almost every car and motorcycle brake line has been made in for decades.
- 45 degrees is SAE, 37 is not. Three titles say 45 and two say 37. The 37 degree flare is an AN and hydraulic fitting, useful on a kit whose other half you do need, and never on its own the brake standard.
- A turret or a case. Two titles count their pieces, at five and eight, and three come in a case. On a tool with dies for several sizes, the case is how you still have all of them next year.
What no title on this page will tell you
- Whether your car takes SAE double or DIN bubble. One title names SAE and one names DIN, and neither can know what is on your car. Look at the end of the old pipe you are replacing before you buy anything.
- Whether it will flare hardened steel. Cheap handheld clamps grip well on copper-nickel line and slip on plain steel. Nothing here says which material it is rated for, and copper-nickel is what most people should be using anyway.
- That the tool is a third of the job. You also need line, fittings, a bender and a way to bleed the system afterwards. Two of the twelve here cover the other parts, and the bleeding is on you.
- A bad flare does not drip, it fails. This is the one repair on this site where getting it wrong is not an inconvenience. If you cannot pressure test and bleed the system properly afterwards, this is a job to pay for.