These connectors are known to fail and pose a fire hazard. The US Consumer Product Safety Commission (CPSC) does not recommend their use. Sealed connectors like AlumiConn are much safer and CPSC approved. The photo shows one of these swivel connectors in my house after an unexpected connection failure, about 12 years after the previous homeowner installed them. I'm in the process of replacing all twister connectors with serrated connectors throughout the house. Save yourself the headache (and risk of fire) and just install the spade lugs.