First time bowhunting. Purchased some mechanicals and although I understand the concept of opening on impact Iam alittle confused. They come packaged with rubberbands on them. Do these little o rings stay on the head and do they break upon impact as the arrow opens up? I took one off and i cant see how the blades would stay together without them.

Please help. BTW do you guys like mechanicals? I am using them because i have only practiced with field tips and I am going out tomorrow and I have had no time to shoot with regular broadheads.

Thanks