They need better tread on the soles. The first one minute of the tracks are just fine, then a SKIP! So, I purchased this, cloned it, and into the computer. Needless to say, this is the last time I am buying anything from Amazons renewed program. Dual density outsole for added stability and support. Was very happy when they arrived pugged them into my computer and got them all charged up. These come in a variety of colors and look awesome with all sorts of outfits. It has the classic round shape other robotic vacuums have. I can’t wait to wear these with distressed jeans! So if you’re between sizes you’d probably be safe ordering a half size down.