Electric Shaver Head Replacement Cassette for Series 9, Compatible for all Series 9 Electric Razors How to replace your shaver head. For older models which have a foil and a cutter block as two independent parts you will need to change the parts in two steps: 1:First remove the foil, either by pressing the release button if your shaver has one, or by pulling the foil. 2:Next rotate the cutter block by 90 degrees and pull it off, holding it at the ends to avoid touching the blades. To fit new parts, simply carry out the same procedure in reverse. Small investment, peak performance. Within 18 months, your shaver will cut an average of 6,000,000 hairs. In accomplishing this substantial task, the cutting parts will gradually wear out and your shave may become less close and comfortable. That's why recommends changing your shaver’s foil & cutter block every 18 months to maintain your shaver’s maximum performance. For an efficient shave every day.