Compatible with: Series 5: 52 S, 52 B, 5020S, 5030S, 5040S, 5050S, 5070S, 5090CC; WaterFlex: 51 B; Replace the old cutting head with a new one for a whole new experience. Easy to use. install and easy to install. Remove without tools. It is recommended that the cutting head be replaced every 18 months.