If you buy a spare aerator 10 internals, you realize later possibly to the non-exchanged mouthpieces damage in the chrome plating (Mouthpiece is the short chrome pipe section with thread). Many of my inner parts were repeatedly to descale (with citric acid) as good as new, but the lime had broken the chrome of the mouthpiece.
Since you can not buy individually the mouthpieces, I recommend buying this spare aerator sets of application and mouthpiece (and poetry).
