The only twist-on for aluminum-to-copper connections.The Twister AL/CU Wire Connector is the only UL Listed aluminum-to-copper twist-on connector that prevents aluminum oxidation while providing a secure connection. Filled with an anti-oxidant compound, the Twister AL/CU easily twists on with swept-wings making a comfortable connection with improved conductivity and cooler connections.The live-action spring expands and contracts with aluminum wire to ensure a secure connection while the hexagonal head makes for quick and easy installation by hand or with a standard nut driver.The Twister AL/CU is the only twist-on wire connector to be UL Listed and CSA Certified for aluminum-to-copper connections, as well as the only twist-on solution to comply with the National Electric Code Section #110-14(b).Twister AL/CU Wire Connectors are designed as a one-use only connection.For use only on copper-to-copper or aluminum-to-copper connections. Do not use on aluminum-to-aluminum connections.