This is the best product ever - if you're wearing a cast. It really truly keeps the cast dry. I swim in a squad & it easily withstands an hour's hard swimming & is BRILLIANT for in the shower. The review saying get a smaller size is right - I am a lady size 10-12 & the large child's one is perfect. It arrived really quickly & requires no maintenance other than to dry it like you would the limb it covers.
You only get one - the review talking about plural of the product should be removed. The top is very hard for my strong 8 year old to undo & even when that's successfully negotiated the contents tend to splurge all over the drinker until they are fully proficient.