This product should be used by all JJCCR divecan hud users.
This hud adaptor made by JJccr is to protect the shearwater DiveCan hud from being held in the wrong position.
If you have one of the narked at 90 hud protectors for the standard hud this adaptor will not fit into the old hud protector but we have developed a new type that accepts both hud with or without the adaptor