The STX Hammer 500 EnduraForm is an updated version of one of the best defensive lacrosse head of all time. So rather than try and play around too much with the deisgn of the STX Hammer 500, STX built up the technology that goes into the head. Starting back with their famous All Climate Performance technology, STX has always been ahead of the game when it comes to building durable heads. The next step in their evolution for maximum durability is EnduraForm. According to their research, heads with EnduraForm have up to 25% added stiffness.This is perfect for any defenseman who is looking for a super stiff head. When you are throwing checks using your STX Hammer 500 EnduraForm, attackmen will remember you after the final whistle.