Commercial grade steady burn C9 replacement light bulbs and lights for intermediate (C9/e17) base sockets. Energy efficient outdoor c9 Christmas light bulbs that only use less than 1 watt will save you money year after year when compared to traditional incandescent c9 Christmas light bulbs. These ultra bright steady-burn c9 light bulbs have a 50,000 bulb life and and are UL listed for indoor and outdoor use. These  LED C9 bulbs screw into our C9 Stringers (25' & 100'), our E17 Heavy Duty Light Strings (25', 100' & 330'), our commercial grade bulk  1000' C9 spools as well as our vintage Twisted Wire Strings with E17 Bakelight Sockets.