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 MAC Encore.

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

Also available for transporting Mac Ultra fixtures

Exterior dimensions: 24"W x 48"L x 42.5"H (height includes castors)

Weight:
Viper Dolly: 119 lbs
Mac Ultra Dolly: 102.5 lbs
Acme Lyra Dolly: 128 lbs
Encore Dolly: 143 lbs