Gen 1 battery cover showing 3 protruding tabs. Right side battery door with continuous ring and larger diameter.
First generation door (left) vs second and third generation door (right)

The second generation housing is an evolution of the previous design, adding improvements to strength and decreasing size. In order to make these improvements, we increased the size of the battery door. Due to this change, the second generation battery door will not fit into existing first generation power meter housing. Stages gen 3 power meters use this same design and thus the battery doors for gen 2 and gen 3 left-side power meters are interchangeable. 

We will continue to offer replacement battery doors and o-rings for the first generation units using the latest stronger, improved materials. If you are in need of a replacement, please open up a support ticket with Stages Cycling or Stages Cycling Europe or visit your nearest Stages Cycling dealer for assistance.