This Clamp-On Holder is designed to be fast and easy to install. It's as easy as placing the holder on your rear axle nut, tightening the allen screw (wrench provided) and then inserting your flag. There are several sizes to choose from, you just need to know the size of your axle nut. If you don't know the size you need, just put a wrench on your rear axle nut and if a 27mm wrench or socket fits your nut, then that's the size you need. It will hold a 1/4" whip pole plus there is an ejection slot (quick release) for easy removal of broken flags.