Developed by engineering students enrolled in the University of Cestlep, the Armour Rating Metric (or ARM) allows combatants to guess the capabilities of armour and ammunition at a glance.
| Unarmoured | ARM 0 |
| Soft (Leather, thick clothing, thin Kevlar) | ARM 1 |
| Hard (Steel or ceramic plate, thick Kevlar) | ARM 2 |
| 8-15mm RHA | ARM 3 |
| 15-30mm RHA | ARM 4 |
| 30-50mm RHA | ARM 5 |
| 50-75mm RHA | ARM 6 |
| 75-100mm RHA | ARM 7 |
| 100-150mm RHA | ARM 8 |
| 150-200mm RHA | ARM 9 |
| 200-300mm RHA | ARM 10 |
| 300-500mm RHA | ARM 11 |
| 500-700mm RHA | ARM 12 |
| 700-900mm RHA | ARM 13 |
| 900-1200mm RHA | ARM 14 |
| 1200mm RHA+ | ARM 15 |
Some types of armour have special characteristics; for example, in the mid-1960s a number of HEAT-resistant composites were developed for use in tanks, such as that in the T-64 Main Battle Tank.