Yes, you can also measure the bottom your bottle. Simply measure the cross-section in the middle of the bottom of your bottle. This will help determine if the FITCHUG BOTTLE-GEAR you are considering will fit your exact brand/ bottle. BOTTLLE-GEAR SIZES 1. 40oz Xtreme SERIES bumper opening is 3.6" wide 2. 40oz PRO SERIES bumper opening is 3.6" wide 3. 64oz PRO SERIES bumper opening is 4.9" wide  For more bottle fitment information also see →BUMPER TECH