The enclosed concept was brought to us by our friends at North Florida Cave Training. We upgraded the design to bring you the RTS "Return To Source" series of reels. The material used is durable Nylon with all Stainless steel hardware. Customization of the reel includes three line color options and two bolt snap configurations. The reel has an exterior tensioning feature to make sure your line does not unwind during the dive. The enclosed body is designed to help prevent entanglements in your line.