Upgrade: Compared to the original model, we lengthened each step by 2 inches and each step is larger, increasing the safety of the product while providing a smoother climbing environment for older or leg-injured pets. Cover added waterproof layer to protect the sponge from getting dirty. Even if the pet accidentally pee on the dog ladder, will not leave a mark on the sponge. Safer,Wider&Deeper Steps:Our dog stairs are excellent for those older dogs who are less mobile as they age or for cats with injuries. More wide and deep steps are helpful for reducing the strain that constantly jumping up and down onto lower bed,sofa can have on your pet's joints,and Topmart dog steps will not shake and slip during use. The cover made of corduroy is more frictional than other covers, pets will not slip on the stairs.