No pre-twisting required on the Wire-Nut® 73B® Wire Connector. The positive grip design provides fast and easy installation. The deep, wide skirt helps protect against flash-over and turned-back strands for maximum dielectric protection. Wire-Nut® Wire Connectors are reusable for easy circuit changes and additions. Tough, UL94V-2 flame retardent shell rated at 105°C (221°F). UL Listed to 486C and CSA certified to C22.2 #188; comply with Federal Specification W-S-610E.