If your installations need to be insulated, the choice is this 3M 8420 Connector Insulator. It doesn't need heat to activate its shrinking capabilities, but it still provides an airtight seal to prevent moisture from seeping in and ruining your wires. This connector insulator is ANSI Certified and RoHS 2011/65/EU Compliant for use in insulating wires and cable splices and a range of applications such as direct buried or submersible, dig-in repairs and secondary splices. It also provides protection for high-voltage, air-insulated connectors or lugs so you get the most use out of it.