A bulletproof vest is made up of a panel, which is a vest-shaped sheet of sophisticated plastic polymers made up of numerous layers of Kevlar, Spectra Shield, or, in some countries, Twaron (similar to Kevlar) or Bynema (similar to Spectra). The name "bulletproof" comes from the idea that these vests can withstand a high volume of bullets without sustaining any damage. These materials are strong and lightweight, which makes them ideal for making protective clothing. They also conduct heat and sound, which helps keep wearers comfortable during cold weather or while listening to loud music. There are two types of bulletproof vests: functional vests and fashion vests. Functional vests are used by police officers and military personnel who need protection against guns with which they are familiar. Fashion vests are worn by security guards at airports, banks, and other places where they do not require protection against firearms. Vests are usually made with elastic waistbands and neckties so they can be fitted properly. Some models also have zippered pockets inside the chest area and open front pockets outside the body for holding items such as radios and walkie-talkies. The outer layer of most vests consists of several panels that attach together with metal snaps or velcro. These panels can be removed if someone gets injured who cannot wear a vest anymore.