It is very important that you replace your keypad membranes at the earliest sign of wear. Keypad membranes are the stickers that protect your keypads (the buttons you push to pour your shots). The keypads (electronic keyboards) that sit behind the stickers are very sensitive and they can be damaged and/or ruined if the keypad membranes get worn and not replaced in a timely fashion. The keypads (electronic keyboards) are pricey items to replace so it makes much more sense to replace the membranes (stickers) at the first signs of wear rather than waiting and then having to replace the actual keyboard(s).
Included are the necessary keypad membranes (stickers), which need to be replaced. Now, these are simply stickers that need to be removed and replaced and it is a very simple process. You simply remove the old ones 13 find a corner you can peel up and then peel off each membrane (sticker). Try to remove as much of the sticky stuff (glue from the sticker backing) as possible before putting the new membranes (stickers) on.