Wiwaplex 50 PCS Heat Shrink Butt Connectors Crimp Electrical Terminals Heat shrink waterproof wire connector Yellow 12-10 AWG Standard crimp and then seal heat shrink butt connectors. Material : Copper + PVC+ Tinplate Dual-walled design, polyolefin tubing in outside and hot melt adhesive in inside. Allows visual inspection, prevents corrosion, and provided a waterproof seal. These work great for automotive, marine, and many other applications.