Standard manual wheelchairs fall into two categories, the self propelled models which have rear wheels generally between 22” and 24”. This allows the occupant to propel themselves using hand rims on the outside of the larger rear wheels. The second type is the transit wheelchair, which have small rear wheels, normally around 12” in diameter which means the occupant cannot propel it.
Added benefit of the self propelled wheelchair is that the larger wheels make it easier climbing kerbs and steps as well as being more comfortable riding over bumps
Use a transit wheelchair where the occupant is not capable of propelling the chair at all, even to just turn around, and there is a fear of hands falling onto wheels