1.PREMIUM COPPER CORE AND HEAT SHRINK TUBE: Made of high quality tinned copper and adhesive lined heat shrink tubing. These professional butt connectors ensure protection against the elements. Heat shrink tubing provides high tensile strength and resistance to stretch and mechanical damage, high thickness copper core ensure protection against the elements 2.PREMIUM SOLDER SEAL RING: Tubing reduces in size, the enough solder will melt and flow through the stripped wires, ensure a long lasting connection for your application 3.BETTER WATERPROOF SOLUTIONS: Double wall design, Hot Melt Adhesive inside ensures wires strongly connected and prevent wires slipping from the terminal; Polyolefin outside tubing provides insulation and improves pullout strength 4.WHAT YOU GET: This wiring connectors kit includes 135 pcs 4 different sizes heat shrink wire connector; Plus 75 pcs 4 different sizes solder seal butt connectors