 This armour, made by the Flintkote Company, was improved through a series of tests and a modified armour of pure quartz gravel in a mastic of pitch and wood flour was designated HCR2.Tests were also conducted to test plastic armour's ability to protect ships from torpedoes with shaped charge warheads but this project was abandoned due to the low probability of these weapons becoming a serious threat and protection of armoured fighting vehicles and concrete fortifications became the priorities.The original plan for tank protection with plastic armour was to produce HCR2-filled steel panels, small in size to reduce the area damaged by a single projectile, which could be fastened to an M4 Sherman in an emergency.