Color-Coded Screw On Wire Connectors for quick connections anytime. Fixed Precise Conical Wire Spring. No Pre-Twisting of Conductors is Required – Spring Creates its Own Thread. Reusable Screw on Wire Connector Threads On or Off splice for fast and easy circuit changes and additions. Tough, UL 94V-2 Flame Retardant Shell will not crack or break, even when applied to maximum wire combinations under extreme pressure.