NSI Easy-Twist Twist-On wire connector. Flame retardant UL 94V-2 thermoplastic shell provides excellent electrical insulation. Temperature rating 105 degrees C (221 degrees F). Fixed, precise square wire spring provides secure gripping of conductors. Deep skirt entry provides protection from flashover and shorts. Sure-grip ribs improve gripping ability and comfort. Compact design ensures proper installation-especially in tight spaces. Threaded tunnel entry guides the wires into the connector easily. Pre-twisting of wires is not necessary. 1,000 volt maximum in fixtures and signs. For copper wire only.