Waist trainers are typically made of latex, a non-vulcanized rubber, which is a strong yet flexible material that, when worn on the midsection, causes you to sweat. Waist trainers are also made of elastic, nylon, and even cotton, which are added to the latex for more comfort.
The rubbery smell of the latex can be a bit off-putting to some people, so if you are one of those, you can opt for a waist trainer made of another material.