Keep a close shave Change heads every 2 years for the best results Every year your blades travel the height of Mt. Everest... 49 times! After such a workout, even the best materials can lose their edge. Retain your shaver's peak performance ? replace heads every 2 years. Super Lift & Cut technology Dual blade system: first blade lifts, second blade cuts for a comfortable close shave. Precision Cutting System Ultra-thin heads with slots to shave long hairs and holes to shave the shortest stubble. Fits Philips shaver models: HQ6425, HQ6426, HQ6423, HQ662, HQ663, HQ664, HQ686, HQ7415, HQ7815, HQ7830, HQ7850, HQ7870, HQ7405, HQ7615, HQ7616, HQ7617, HQ7814, HQ7816, HQ7817, HQ7820, HQ7821, HQ7825, HQ7829, HQ7845, HQ7864, HQ7865, HQ7868, HQ7885 The ideal replacement frequency depends on your shaving frequency and the thickness of your facial hair. So replace your shaving head in time and stay on top of your game. Philips shaving heads are made of the highest quality steel because they are in regular contact with your skin. However, even the best materials wear down because of regular use. Even if an immediate drop in performance is not noticeable, your shaving head will gradually become less sharp and precise.