The resulting spring-action joint offers a leak evidence seal and resistance to vibration. Flareless fittings do not need a flaring operation and are utilized on medium to large walled tubing. This also relates to the material – all parts with the fitting assembly needs to be exactly the same material. http://donovanoyiow.tinyblogging.com/How-Much-You-Need-To-Expect-You-ll-Pay-For-A-Good-sae-flareless-fitting-28378694