These connectors, once heated, dispense solder to the wires being joined via an internal fluxed solder ring establishing the best chance for a reliable connection. No crimping is required. Heat Shrink is adhesive lined and color coded to industry standard wire gauges transparent heat shrink sleeve allows for precise visual inspection greater pull strenght when compared to PVC or nylon insulated butt connectors protect against corrosion due to fully Waterproof seal rated for 1000 volts and 125°C with a 2 to 1 shrink ratio.