For foot sleeves and foot braces, our general advice is to purchase the size sleeve that most closely corresponds to the shoe size you wear most often. If you typically wear a Men's 10 shoe and your sleeve size options are for a "Men's 7-9" or "Men's 10-12," you should go for the "Men's 10-12" size. Foot sleeves fit snugly in order to best support the foot, and in general we never recommend sizing up or down for a tighter or looser fit. However, if you're between two sizes, we do recommend sizing up. For sleeves and braces worn on other parts of the body, such as the knee or calf, look closely at the product sizing instructions and size chart, then order the size that most closely matches your own body's measurements.