Ginsco 100pcs Insulated Heat Shrink Waterproof Butt Connectors Wire electrical 10-22 AWG Kit Dual-walled design, polyolefin tubing in outside and hot melt adhesive in inside. Allows visual inspection, prevents corrosion, and provided a waterproof seal. Standard crimp and then seal heat shrink butt connectors. These work great for automotive, marine, and many other applications.