Not all underwear buttons are metal, some are plastic. 1. There are many kinds of underwear buckle points, single row, double row, three rows or even four rows. These buttons can firmly lock underwear, so you don't have to worry about falling off after wearing them, and the tightness can be adjusted freely. 2. Underwear buttons can gather the bra and won't slip after wearing it. In the underwear design on the market, there are three positions of underwear buttons, some are designed at the back, some are designed at the chest, and some are designed at the side of the body. 3. Button underwear is also the most common kind of underwear. The average girl wears underwear with buttons every day. There are many kinds of buckle underwear. According to the number of buttons in the back row, underwear can be divided into 1-5 buttons, and different buttons are suitable for different chest types. According to the appearance style, it can be divided into rimless underwear, sports bra, seamless underwear and long-bundle underwear.