The only mech. heads I use are Razortips from Grim Reaper. They fly great, and they don't have any o rings. You might want to try the G5 Montec heads if you stay with fixed. They fly great, and right with my field points out to 40 yards. That is as far as I have ever shot them.And a lot of people like theSlick Tricks, they say they fly great too. Good luck.