D'avin says of the 'little colonel' hand grenade, "Carbide casing. Undetectable to weapon scanners." The writers are a bit confused. There are metalic carbides, like tungsten carbide which is used for super hard drill bits and cutting tools. These materials are electron dense enough to show up on contemporary airport scans. Carbonates, thermoplastic polycarbonates, don't show up very well on x-ray scans or metal detectors and are used in the new lines of 'undetectable plastic guns' .