Fits any blaster with an N-strike barrel attachment point. It’s snug on a Stryfe, there’s a nice tight clearance with the barrel attach point on the blaster, with no wiggle at all even when jostling the blaster around. Count up and count down functions are simple enough. I can’t speak to how well calibrated the speed readings out of the barrel are, but it effectively captures barrel velocity differences between the stock and modified blasters I own. For reference: stock Stryfe with used Elite darts was reading about 55 fps on average. Modded Stryfe with Neo Hellcats, 42.5mm cage, and running on a 3s LiPo were measuring anywhere from 130-150 fps. Fun to quantify the improvements in performance on both flywheel and springer mods!