Foil and Cutterblock. Suitable for our Series of 1 razor blades should be replaced every eighteen months. Replacing your blade gives a 25% better shave. For optimum performance and clean regularly. Back 100% performance. Braun replacement foil and cutter blocks help to maintain your shaver's peak performance. Therefore Braun recommends changing the blades every 18 months to maintain your shaver as parts of gradually wear over time, and your shave may become less close and comfortable fit. After the replace them you get 100% of the performance to your shaver