Gadjit Cup Keeper - Car Cup Holder Adapter (Black) Expands Cup Holders to Hold Mugs, Convenience Store Cups, Water + Soda Bottles with up to 3.6" diameter, Fits Yeti Rambler 20 oz 30 oz Want to Easily Expand your Vehicle's Cup Holder? Try Cup Keeper! Holds mugs, convenience store cups, and bottles No tools required. Dimensions: 3.6" diameter top of cup, 3.375" diameter bottom of cup. Portable -- move from one vehicle to the next. No installation need -- simple sits in your standard cup holder