The mount remains the same for units that utilize the "Z" Foam and Cartridge. Most XL2's are available with this new, super convenient method for stamp assembly (Model XL2-55,305 & 325 are not available with "Z" Foam and Cartridge). "Z" Cartridge reduces your inventory commitment of cartidges by 80%. "Z" Foam and Cartridge allows you to ink your own cartridge when the foam and cartridge are already in place. Say good-bye to the scissors, tweezers and ink bag. Say good-bye to the inventory hassles attributed to managing many sizes and colors pf pre-inked cartridges. Say hello to complete inventory flexibility and to significant cost savings. How did we reduce your cost without sacrificing print quality? First, the "Z" foam is now 2 layers. The first layer is the same foam we always use, just thinner (less cost). It has been adhered to a thin "hard" cartridge (same material we use now). Second, you are now inking your own cartridge and avoiding the upcharge of us inking it for you. Third, your ordering, receiving and inventory control procedures have been simplified. A couple of added bonuses... due to the thin layer of foam and it being adhered to the cartridge (no chance of air pockes that slow migration), ink migration is now 30-60 minutes."Z" Foam is priced 20% less at end column than standard XL2 foam. "Z" Foam and Cartridge....raising the bar to a whole new level.