This Emperor Aquatics Replacement Quartz Sleeve fits all Emperor Aquatics 40W UV Sterilizers manufactured after 1998. The outside diameter of this Quartz Sleeve is 1". Pre-1998 sterilizers have a different Quartz Sleeve, which we do not carry. It also fits the 80 Watt Smart UV Sterilizer, Part# 02080. The 80 Watt takes two 40 Watt Quartz Sleeves.