I have used the grim reapers for 2 seasons now and I have to say they done the job for me. I used to use NAP spitfires but I was getting some shots they I felt should have been easy pass throughs that didn' t so I decided to try the reapers and I am glad I did. As 5shot said on the spring after repeated shots the spring does break or gets to weak to hold the blades closed. Every shot I have made with these heads has been a pass through or a complete miss(operator error), I have used them on three bows a 60lb Reflex xpress, Bowtech patriot s/c 60lb and a 70lb Bowtech Pro38 dual cam. They opened just fine on the lighter weight bows and didn' t open premature on the fast pro38 dual cam. The only problem I had with this head was the first year I shot them the furrlow in the bottom skirt area would bend from the blades putting pressure on it but last year they changed that part of the furrlow from Aluminum(sp) to metal and that solved it. They also fly very well and I have only used them to hunt deer but that is all I hunt. Give a try you might really like them.