Micropore has switched to a production process that causes their ExtendAir EP Cartridge to have a slightly larger bore center tube spindle. The larger bore spindle must not be used in the O2ptima without an adapter. All O2ptima divers must have one of the O2ptima Premix Rod Adapters. The latest version of the adapter has been redesigned to be easier to grip when removing from the cartridge. In the video Dive Rite's founder, Lamar Hires, explains the differences and how to use the large bore cartridge and plug with your O2ptima.