It is a device which is shaped like a standard firearms cartridge but contains no primer, propellant or projectile.
Dummy round is designed to be a fake cartridge from the very beginning.
It serves the same function as a dummy round, but different in that a dummy is usually made from a real cartridge with its propellant and primer removed (still has the projectile and the casing).
.22 LR, Aluminum Alloy, Red Anodizing Finish, w/ Sling, 6 Pieces in 1 Pack