If you use these neat lil gizmo's, be sure to test your setup. On my Phoenix, they were sliding up onto the vanes in flight and yes, I had the right size. The fix is a small rubber "O" ring behind the grappler. W/ my Emax, they are a waste of time and $. They work great for me at about 290 fps and w/ the Max at 330, they blow right through the bird. You Ecet guys are gonna be somewhere inbetween. I found no change in poi at 30 and they weigh about 20 gr, this is w/ Slick Trick 100 gr bheads.