Collenchyma cells are not thin-walled at maturity. While they are living at maturity, collenchyma cells have thickened, unevenly thickened cell walls. These thickened walls are a key characteristic that distinguishes them from thin-walled parenchyma cells, which are also living at maturity. 

Sieve tube are thin-walled and living at maturity. While they are alive, they lack a nucleus and other organelles, relying on companion cells for support and other functions.

Also,xylem vessel are not thin-walled or living at maturity. In fact, they are dead cells with thick, lignified walls that form a continuous tube for water transport. 

Sclerenchyma cells are not thin-walled and living at maturity. They are characterized by thick, lignified cell walls and are dead at maturity.