This is an adaption of Coxmate's Sculling Mirror which has been used by many thousands of rowers around the world for many years. It is very rugged, easy to adjust and uses a large diameter (48mm/1 .9") scratch resistant glass mirror. It can be mounted onto the peak of a baseball style cap or attached to helmet with a clip which is fitted to the helmet with double sided tape (supplied). The mirror is easily removed/refitted to the clip.