This Replacement filter Cartridge replaces Unicel # 6473-164 and complies with OEM # 6473-164 specifications. This 18 ¾ inch long and 5 11/16 inch wide filter is actually Inner microclean filter for the Sundance Spas Ultra Filter. This cartridge fits into the outer pleated cartridge part AK-6473165. It provides you clean and clear water for your spas and pools. By installing this filter cartridge you get complete protection from dust, sand and worms.