ErgoWear Underwear is crafted with flexible materials that allow a much wider range of sizes for you than typical underwear. Depending on the fit you desire, it is possible to have up to three sizes available. Please use the size chart below to determine the best size for you. The fit will depend mostly on three variables of your body. The first is waist size which is what you normally wear. The second variable is the size of your junk and the third is your thigh width for trunks and boxer briefs. For example, if your package is larger than average and/or you have larger thighs, choose a loose fit. If you are smaller than average, choose a tight fit. Otherwise, simply choose a normal fit size for you.