Severne harness lines are made with long lasting clear 2mm thick, high density PU tubing and strong nylon webbing (not poly-pro!) for increased UV resistance and less wear. The clear tubing lets you know when the line needs to be replaced (more windsurfing and less swimming!) as opposed to opaque tubes you can't see through. Made to stay in position and not swing around when you're hooking in & helps prevent unintentional hook-ins & catapults. Durable, strong & safe.