Combining ergonomic design with rugged, lightweight practicality, steel-frame Rock N' Roller multi-carts can transform into any of eight configurations in seconds, eliminating the need for different types of carts. Foldable sides rotate and lock into place by release cables, instead of the old-style removable pins. The Rock N' Roller has become the #1 selling cart or dolly in music history.Rock N Roller ModelsR2 Micro:This compact model weighs only 18 lbs. and carries big loads up to 350 lbs. Its frame telescopes from 26.5 to 39 inches in length with 25/20 inch (front/rear) foldable sides. It uses 6 x 1.75 inch rear wheels and 4 inch x 1.25 inch front swivel casters.R6 Mini:This compact model weighs only 25 lbs. and carries big loads up to 500 lbs. Its frame telescopes from 28 to 42.5 inches in length with 24-inch foldable sides. It uses 8 inch x 2.50 inch rear wheels and 4 inch x 1.0 inch front swivel casters.R8 Mid:This compact model weighs only 29 lbs. and carries big loads up to 500 lbs. Its frame telescopes from 34 to 52 inches in length with 32-inch foldable sides. It uses 8 inch x 2.50 inch rear wheels and 5 inch x 1.25 inch front swivel casters.R10 Max:This compact model weighs only 31 lbs. and carries big loads up to 500 lbs. Its frame telescopes from 34 to 52 inches in length with 32-inch foldable sides. It uses 10 inch x 3 inch rear wheels and 5 inch x 1.25 inch front swivel casters.