Marine grade and designed for connecting different wire gauges. The gauge is marked on each end of the connector and also displays a corresponding color band. 99.9 % pure copper with seamless tube, tin plated. Proprietary nylon/polyolefin 3:1 shrink ratio tubing with adhesive lining provides maximum clarity for wire inspection purposes, faster shrink times and improved abrasion resistance. Simply insert the wire, crimp and heat shrink for a complete environmental seal.