What separates the Mia and Mia Thermo bottles from the other bottles is that there's no plastic materials whatsoever used in the manufacture of these bottles, from their cap to their base, that's why they're totally plastic free.
Other than always ensuring a totally fresh and clean taste on the liquid they contain, steel bottles are a great investment to hydrate while cycling and in everyday life, at work or at the gym, and are a conscious, eco-friendly choice: steel is one of the most recycled materials and a stainless steel bottle can be used for years on end.