This is Aguila .22 Long rifle Colibri ammo. This was the original quiet ammo, and has been very hard to get in the past. There is no gunpowder in this round, It is propelled solely by the priming mixture. It is completely quiet, all you will hear is the firing pin drop. This ammo will not cycle semi-auto weapons, you will have to hand cycle the bolt. This ammo travels at 375 FPS. This ammo in packed in 50rd. boxes, 500rds. per brick.