is among the oldest forms of personal protective equipment, and is known to have been worn in ancient India around 1700 BC and the Assyrians around 900 BC, followed by the ancient Greeks and Romans, throughout the Middle Ages, and up to the modern era. Their materials and construction became more advanced as weapons became more and more powerful. Initially constructed from leather and brass, and then bronze and iron during the Bronze and Iron Ages, they soon came to be made entirely from forged steel in many societies after about AD 950. At that time, they were purely military equipment, protecting the head from cutting blows with swords, flying arrows, and low-velocity musketry. Some late medieval helmets, like the great bascinet, rested on the shoulders and prevented the wearer from turning his head, greatly restricting mobility. During the 18th and 19th centuries, helmets were not widely used in warfare; instead, many armies used unarmored hats that offered no protection against blade or bullet. The arrival of World War I, with its trench warfare and wide use of artillery, led to mass adoption of metal helmets once again, this time with a shape that offered mobility, a low profile, and compatibility with gas masks. Today's militaries often use high-quality helmets made of ballistic materials such as Kevlar and Twaron, which have excellent bullet and fragmentation stopping power. Some helmets also have good non-ballistic protective qualities, though many do not. The two most popular ballistic helmet models are the PASGT and the MICH. The Modular Integrated Communications Helmet (MICH) type helmet has a slightly smaller coverage at the sides which allows tactical headsets and other communication equipment. The MICH model has standard pad suspension and four-point chinstrap. The Personal Armor System for Ground Troops (PASGT) helmet has been in use since 1983 and has slowly been replaced by the MICH helmet. A ballistic face mask is designed to protect the wearer from ballistic threats. Ballistic face masks are usually made of kevlar or other bullet-resistant materials and the inside of the mask may be padded for shock absorption, depending on the design. Due to weight restrictions, protection levels range only up to NIJ Level IIIA. Torso A ballistic vest helps absorb the impact from firearm-fired projectiles and shrapnel from explosions, and is worn on the torso. Soft vests are made from many layers of woven or laminated fibers and can be