Easy-on, easy-off without tools. Wings are knurled for a surer grip and offset from the centerline for greater twisting leverage. Easily removed for repeat usage on same size combination or larger. Expandable square-wire plated spring instantly adjusts to the shape and size of the splice for a vibration-resistant connection. Tough thermoplastic shell shields against environmental extremes. Flame-retardant, non-porous and non-corrosive shell resists surface cracking and chemical action. Temperature rating: 221 degrees F. Superior flash-over protection. High-dielectric shell features deep skirt design to prevent exposure of bare wire. Buttress threads screw into wire insulation. Copper to copper connections only. cULus Listed.