I guess the question is what size feet you have and the type of sneakers. I wear a size 9 or 9 1/2 (or 42/43) shoe and can use a size up in booties for my mtb shoes from what I use for my road shoes. I am also able to get the size larger booties over several different pairs of sports shoes, but don’t generally use them because I don’t have booties with durable soles (my major complaint with booties in general). I had purchased a size XL PI AmFib mtb bootie that turned out to be way too big for any of my shoes, including sport shoes.
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