Short answer: no, not for the brake hydraulic circuit itself. Compression fittings show up on brake lines more than they should, usually because they’re easier for a first-timer than learning to flare, but they’re not built for what a brake line actually does.
Why compression fittings are the wrong tool here
A compression fitting seals by squeezing a ferrule down onto the tube under a nut. It works fine on things that see steady, moderate pressure, fuel lines, coolant, air lines. A brake line doesn’t see steady pressure. Every time the pedal is pressed, the line sees a sharp pressure spike, and it sees that thousands of times over the life of the car, on top of constant vibration from the road. A compression joint can hold under that for a while and then work loose gradually, often without an obvious external sign until the pedal goes soft or the line lets go. A flared joint, the tube itself formed into the seal, clamped by the fitting rather than relying on a ferrule biting into the outside of the tube, is what brake systems are built around for exactly this reason, and it’s what every OEM brake line and virtually every aftermarket fitting is designed to mate with.
What to use instead
SAE 45° double flare or ISO/DIN bubble flare, depending on what the vehicle calls for, made with a real flaring tool, not a compression fitting improvised into the role. It’s a five-minute-per-joint job once you’ve got the right tool, and it’s the difference between a brake line you install once and one you’re back under the car checking on.
What we stock
BrakeQuip Products carries the flaring tools to do this properly, BQ350 and BQ351 cover SAE, AN 37°, and DIN flares, along with the matched fittings and copper-nickel or stainless tube to go with them, so there’s no reason to reach for a compression fitting on a brake line in the first place.