I've had wasp mechanicals open on my Exocet until I used two o'rings. I didn't believe it after reading about it on another forum until I saw it myself. Maybe its because the Exocet is a recurve and the string release is at it's highest weight at that point(I imagine that the bolt accelerates pretty violently), but maybe its because the way the Wasp is made or maybe I didn't have the bolt seated on the string. Who knows, I've not tried many mechanicals but I will stick with the Wasps and two o'rings.