A wheeled dolly used for transporting various fixtures. Also refered to as a fixture cage.
Pictured above is the Mac Viper Dolly, other fixtures which travel in this style of dolly are Martin ERA 800, MAC Encore, Xtylos.

Exterior dimensions: 24"W x 48"L x 39"H (height includes castors)
Internal handing hardware configurations differ depending on the type of fixture being transported.
4 castors

Weight:
Viper Fixture Dolly: 119 lbs