The V50 test is the internationally recognized standard for assessing the fragmentation resistance of personal protection.  The fragmentation test is conducted using Fragment simulating Projectiles (FSP's), which are available in a range of weights approximately following the binomial progression. 

The test is conducted by firing FSP's at the armour at increasing velocities until an average velocity of penetrating and non-penetrating projectiles is obtained.  The higher the ballistic speed, measured in metres per second, the higher the rating of material, shown as V50 000m/s. 

The V50 (Velocity 50% or mean velocity) is the average of the velocities recorded for six fair impacts consisting of the three lowest velocities for complete penetration and the three highest velocities for partial penetration, provided the spread is not greater than 40 meters/second (STANAG 2920).