EcoVessel Boulder Style 2-Piece Replacement Screw Cap for Newer Boulder, Bigfoot, Growler and Twist Bottles with Strap Drinking made easy -the wide opening is for easy filling, and the small opening for easy drinking. Add your favorite Fruits or ice to add natural flavoring to your water CREATES A TIGHT SEAL - EcoVessel Replacement Stainless Steel Dual Top fits with the newer Boulder, Bigfoot, Growler and Twist bottles; this part comes as one piece and is sold as a unit VARIETY AND STYLE - The EcoVessel Replacement Stainless Steel Dual Top comes in different colors to choose from; mix and match according to your taste and your favorite EcoVessel bottle Leak proof and easy to carry - simply toss your bottle in a bag and go! the dual top creates a tight Seal to avoid leaks and makes carrying the bottle around easier with an integrated carrying strap