Replacement metal/ceramic disk fits most 20 mm foggers. Replace disk when fog is reduced or mixed with water droplets. Average life span of a disk is about 1 year if the fogger is used only several hours a day and if the disk is kept clean. Life span is reduced if calcium and algae buildup are not removed. This disk will fit any fogger/mister using the 20mm (approx 13/16") disk. Can be installed using wide bladed tool sometimes included with the fogger or use screwdriver or knife. Remove protective rim if present before installing.