Added strength around interior stacking shoulder which increases resistance and durability. Internal ribbed vents allow for smooth removal of garbage bags thereby reducing the risk of back injuries. Reinforced for added strength and durability. High impact plastic is crush resistant, rugged and long lasting. Lock down lids snap securely in place allowing contents to remain within, in case container is overturned. Rims are reinforced for added strength and durability. Handles have increased wall thickness and are designed for easier lifting. Built-in wheel assembly. Base is reinforced to provide greater stability and weight distribution when dragging over surface. Dollies are sold separately.