Alex from Adaptado.es did a review of RehaDesign wheelchair tire covers. While my Spanish is not really very good, I was able to understand his review with the help of Google Translator. One thing that Alex points out is that they "are elastic and even someone with very little strength is able to put them without help". Another thing he mentions is that there is little or no slippage. This is thanks to a foam type material on the inside of the covers which holds tightly to the wheels.
Read the review in Spanish, or see the English website for more information about RehaDesign Wheelchair Tire Covers.