The Drotto auto boat latch system is constructed of heavy gauge steel that has been zinc coated to prevent rust. The zinc coating also makes the Drotto auto boat latch extremely strong, durable and weather resistant. We have lined the contact surface between the boat and the auto boat latch with a hard, smooth plastic liner to prevent damage to your boat's surface. The 3-3/4" boat latch works with trailers that have a bow roller that measures between 3-3/4" and 4". The 3" boat latch version works with trailers that have a bow roller that measures 3". The Drotto product was originally designed with the extremely popular Shorelander trailer but fits many other trailers as well.