MSW Seltzer Mount - CO2 and Bottle Cage holder with 27.2mm clamp BlackMSW Seltzer Mount CO2 and Bottle Cage holder with 27. 2mm clamp Black. The Seltzer mount is designed to carry a standard bottle cage and two threaded CO2 cartridges in a clean and compact way. Holds one standard bottle cage Acomodates two threaded CO2 cartridges up to 25g TECH SPECS Color Black Bottle Type Standard Access Style Top Mount Type Bolt On Defined Color Black