DESIGNED TO LAST: Wings are knurled for a sure grip and offset from centerline for greater twisting leverage. Square wire spring grabs and holds wires for secure connections. DESIGNED TO LAST: Square-wire zinc-plated spring instantly adjusts to the shape and size of the splice FLAME-RETARDANT TEMPERATURE RATING: Flame-retardant properties resist heat distortion up to 105°C / 221°F HIGH-DIELECTRIC: shell features deep skirt design to prevent exposure of bare wire - COPPER TO COPPER connections only STANDARD RATING: 600V max in building wire and at 1000V max in lighting, fixtures/luminaries and signs Unsurpassed quality and durability in a high-leverage, easy-on wing-type design Wing-Gard finger-pleasing 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 Secure connections mean positive continuity The expandable square-wire plated spring instantly adjusts to the shape and size of the splice, then bites down to thread onto the wires without ratcheting and creates a strong, vibration-resistant connection-no pre-twisting tools are necessary