No doubt these would be leak proof because my kids can’t even drink through them with the rubber insert. I tried to and I had to forcefully suck to get the tiniest bit out. We took out the rubber and use as is. Otherwise, nice concept. Sublimated very nice.
Still waiting for delivery and it's 2 days late they said they can't find my house. Hmm never had this problem before with anyone else... PISSED OFF CUSTOMER.
Great quality, fast shipping and they sub perfectly!
Thanks for the help and fast shipping