3M Scotchlok™ 63405 Butt Connector Heatshrink Seamless 22-18 AWG Red with transparent heat shrink tubing covers the seamless barrels to create a seal that blocks water, salt and other harmful substances after you perform the crimping and heat shrink. They are pre-insulated with red vinyl to provide color-coding for fast, trouble-free identification of the required wires. The tubing on these butt connectors also delivers excellent stress relief and improved pullout strength once they've been shrunk.