FIN GEAR rail mounts come in two sizes 7/8” , 1”. They are made of solid aluminum and attached without drilling holes in your boat. The mount simply wraps around both sides of your boat rail and tightened with stainless steel screws. The FIN GEAR mounts can then be attached to the rail mounts by using the thumbscrews. This makes it easy to remove your mounts quickly for storage or put your boat cover on to protect it from the elements.