Designed for the automotive industry these mechanics rough service bulbs last twice as long as ordinary bulbs. Heavy duty tungsten filaments absorb shock and abuse. Made to give 2000 hours of service. Bulbs are 115 volt with the exception of part no. 9700 which is 12 volt. Available in regular or silicone coated in the 75 watt bulb. Tuff skin bulbs protect against shattered glass. Sold by each, packaged by six.