The Moun%ng Blocks a ach to the wheelchair tubing / frame, and they hold the Arms. Product codes and sizes are shown above. The MBR-UE is a pair of universal Moun%ng Blocks which can be used for mul%ple sizes, and is used when the exact diameter of the wheelchair back tubing is not known in advance. If tubing sizes are larger, i.e. 25 or 32mm, then