Foil and cutterblock.. Fits Series 1 shaver models. Blades should be replaced every eighteen months.. Replacing your blade gives a 25% better shave. For optimum performance; clean regularly.. Brings back 100% performance. Braun replacement foil & cutter blocks help to maintain your shaver’s maximum performance. Braun recommends changing your shaver’s blades every 18 months as the cutting parts will gradually wear out over time, and your shave may become less close and comfortable. After replacing them you get back 100% of your shaver’s performance.