Thus your shaver sound almost as good as newReplace all 2 years the shaving heads for optimum results. In two years cutting your shaving heads 9 million beard hair in your face. Replace the shaving heads to get back 100% performanceReminder functionThe latest shaver from Philips have a built-in memory function in the form of a shaving unit symbol. This symbol lights up and indicates, if you need to replace the shaving heads.Simple replacement1. Open the shaver with the unlocking button. 2. Remove the retaining rings by turning it counter-clockwise. 3. Remove the old shaving heads out, and carefully insert the new; make sure that the shaving heads are aligned exactly. 4. Insert the retaining rings on again and secure it in place by turning it clockwise;. 5. If you use the shaving head close properly, you can hear it click into place.So setzem your shaver backAfter you have replaced the shaving heads, you can use the reminder function by pressing the on/off switch for longer than 7 secon