Using the standard 351 size pick, Phil Everly (of The Everly Brothers) added a star shaped cutout where your thumb and finger meet, for the perfect no-slip grip. This was originally a 5 pointed star, but this proved uncomfortable, so was changed to the 10 point. Prior to developing these picks, the Everly brothers worked for Joe Moshay hand finishing his picks. It's clear to see that the Moshay pick is the inspiration behind their design! See here.