With some extra steps, works well with pre-flared tubing. I used on a set of GM replacement brake lines in nickle-copper. They were pre-flared with the nuts already assembled.Using a 3mm Allen wrench, remove the eight screws to split the tool in half. The tubing will snap in between the wheels with a bit of effort. Reassemble the tool halves and tightened the removed screws. Then use the tool as normal. Repeat the disassembly to remove the straightened tubing.