I never actually used it. I attended a class put on by G.E. many years ago when they were going to use Lokring for all refrigerator, freezer and window A/C repairs. The tubing at the connection must be perfectly round. If you prep everything like they say I think it works well. The tool is expensive and so are the fittings.
Challenge yourself, take the CM test --- Certificate Member since 2004 ---Join RSES ---the HVAC/R training authority ---www.rses.org