In most cases the only difference between holders is the position of the rib lock. That is true if you compare AWB and S&S holders in 7X17, 8X20 and 12X20 size. Even the position of the rib lock with a certain brand may vary because of adjustments already made for existing cameras.
Originally Posted by RobertP
In any event, making sure that the rib lock drops into the groove on the camera back is the single most important thing one needs to do in buying holders for an existing camera. I am happy to provide assistance to anyone who has questions about this.