I use NAP spitfire 100 as does my wife.we have great success with them.never had any kind of problem.there are no O rings or rubberbands.
I made one bad hit with the spitfire andf hit a buck right on the shoulder bone at 20 yards.it looked like an 0-6 had hit him.both shoulders were busted and the bolt stuck in the ground on the other side.
I had posted the pic's. of the bones and legs.I could not believe the damage it did.
I went to the carbon arrows also.the tow together is for me the best setup I have found.