Slots are slightly tilted so the bottles fit snugly. Fits pergect! Probably need extra wide next time. LOVE ♡ THESE CROCYS What I call them. It works for me but if you are expecting premium – like metal – these don’t have it. TL;DR; I returned them after about two weeks of use. I love that they are adjustable since straps run between rubber sole, so you can adjust each area to fit. They fall off when you walk and I ordered the correct size of shoe. Not tinny and not too much bass (although I do tend to the bass-heavier side of the fence). 5 out of 5 overall considering the price tag.