When you're buying a suit, you want one that fits perfectly, not just right now, but for the long haul. For your next suit, look for a waist extension tab for a more comfortable -- and adjustable -- fit around your waist and crotch. As mentioned in this video by GQ, even less expensive suit brands are starting to offer waist extension tabs on their suit pants. This feature helps keep your suit pants at the right spot on your waist without having to use a belt, and can be adjusted if you gain or lose a few centimetres over the years without you having to buy a whole new suit. You probably can't have one added to an existing suit, but even if you're looking for new formal slacks to wear under a blazer or jacket, it's worth keeping an eye out for.
4 Easy Suit Upgrades for Under $100 [GQ (Youtube)]