The most widely cited standard for armor is its CE rating: level 1 (lower protection) or level 2 (better impact absorption). The criteria for levels 1 and 2 vary by intended use – back protection, air bag vest or body armor each have different requirements. The CE standards also classify the surface area that armor protects. For example, body armour is classed as type A (limited coverage) or type B (better coverage). And back protectors are classed as either Centre Back (CB) – which offers no protection to the shoulder blades – or Full Back (FB) coverage.