2-in-1 Protective Silicone Boot for Stanley Cup 40oz&20oz/Hydro Flask 12-24oz,Anti-Slip Tumbler Bottom Bumper Sleeve Protector Cover for All Bottles Bottom Width of 2.87-3.56in. ♥ Perfect Compatibility: Designed for Stanley Quencher Adventure (40 oz), IceFlow (20 oz), and Hydro Flask bottles (12 oz/18 oz/21 oz/24 oz).
eBay