replacement Raypak Flange Gasket; Size: 1.5"header for the heat exchanger. This item is designed to fit Raypak pool heater models such as the RayPak Versa and Gemini Pool Heaters. G-304 is the generic equivalent of Repack 800013B gasket. Fits Repack Gemini 53 A/B and Versa 055 A/B, made from 1974-1989. Also Fits 105A, made from 1991-1999. Also Fits Repack model 151, made from 1974-1981. Also Fits 153 and 153A, made from 1981-1987. Also fits Versa 155A, made from 1987-1991.