The CG634 is the Canadian Armed Forces’ main combat helmet. It was introduced in 1997 and is based on the French Gallet TC-3 helmet. The helmet has protection Level 3a rating, which means it is able to stop a shot from a .357 Magnum.
History: The Canadian military sought a replacement for the steel M1 Helmet in the 1980s. In 1984 it trialed the British Mk. 6, the American PASGT, and the Israeli OR402 composite helmets to determine the best 
characteristics of form, fit and ballistic protection. A concept design was developed and the Barrday Co. of Cambridge, Canada received a contract to produce over 2,000 Spectra helmets between 1988 and 1990 for ballistic, engineering, and user trials.
From 1997 to 2004 the CG634 was manufactured by Gallet in Saint-Romuald, Quebec.
Design: The CG634 is made of Aramid (Kevlar) and has a minimum v50 of 634 m/s (compared to the PASGT’s 610 m/s explanation below.) It mates a modified French design, based on the PASGT, but adapted for compatibility with Canadian equipment (head-set, respirator, vision devices, and armoured vest). The CG634 has a 3-point chinstrap with flip down adjustment pieces.
The CG634 has a somewhat similar shape and is sometimes mistaken for the later United States Army’s MICH TC-2000 Combat Helmet. When necessary, a night vision goggle mount is issued.
Helmet testing: The National Institute of Justice test protocol identifies five levels of ballistic performance determined by what caliber and at what velocity a bullet punctures the ballistic material and/or causes blunt trauma to the wearer. “V-50″ or” Velocity-50%” – The velocity of the bullets where 50% of the bullets DON’T penetrate, and 50% of the bullets DO penetrate is the V-50 rating for that ballistic protection.