KiJudo Airsoft does a review of the affordable GBR Impact Airsoft Grenade that is made of ABS plastic. It has a 5-second reset after pulling the safety pin and is reuseable wih no need for any gas power source. It has a maximum capacity of 130-BB rounds can can also be used with water gel ball... "Today we will look at the manual GBR grenade. This airsoft grenade is spring driven, so it only needs springs to propel it."