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Measure your waist Select your cup based on your waist size. Choose a shape that you think will be comfortable for you. Pick a model with a thicker gel lining if you have sensitive skin.
or check the tag on a pair of pants that fit. To figure out your waist size, take a measuring tape and wrap it around your hips where you wear your pants. Wrap your measuring tape with the end under your belly button and pull the rest of the tape tight around your body. Keep it parallel to the floor and read the number where the two lengths overlap to get your waist size. You can also check a pair of pants that fit you well and simply read the tag.  It doesn’t matter if you’re off by a little bit. Cups are sized to fit a range of waistlines. You can actually do this while wearing your shirt if you want. Jock straps and compression shorts are typically worn over underwear, so the extra fabric won’t change anything. Go to an athletic or sporting goods store. Look for a cup that corresponds with your waist size. If they don’t list the waist sizes on the packaging, use the general sizing recommendations to get a size that will fit you.  As an additional guideline, pee wee sizes are usually for boys aged 5-7, youth sizes typically fit boys aged 8-12, teen sizes are for boys aged 13-17, and adult sizes are for men 18 and older. If you’re an adult with a waistline smaller than 28 in (71 cm), start with a teen’s medium. Children older than 5 should wear a protective cup if they’re engaged in contact or physical sports. Cups have a few different shapes, but they aren’t really radically different. One style is shaped more like a crescent moon, while the other common design is a little more form-fitting. Every style of cup will provide the same level of protection so long as it fits right and covers your entire genitalia. Choose a design that looks and feels  comfortable to you.  You won’t be able to try a cup on over your underwear before buying it, but you can try it on over your shorts in the store. You can always go back and get another one if you don’t like the style you’ve picked. Cups aren’t particularly expensive. The edge of a protective cup has a gel lining so that the edges don’t chafe your skin. If you have sensitive skin, get a cup with a thicker gel lining. This will ensure that the cup doesn’t cause you skin irritation while you’re wearing it.  There are foam cups that use a softer material than the traditional hard-shelled plastic. These cups are a great option for children, but don’t offer as much protection. Some cups are machine-washable. If you want an easier time cleaning your cup, read the label carefully to see if it can be cleaned in a washing machine.