ZH-ZYQ type Freefall Freefall Brain Injury Brain Injury blow is hit by the free fall is the principle of making a hit, host for the production of animal models of brain injury. Freefall brain injury model consists of the firing pin hit, falling against stick, metal casing and brain locator four parts. Firing pin diameter 4.5mm, height 20mm, blow bar and 20 g weight 40 g are two kinds of metal casing height 27cm, brain locator includes a base plate, rat adapter, mouse ear rods and so on.