Im not sure what they mean by that. These are comfy but they wore out immediately. Hydrate as much as you can. These are shockingly comfortable and well made. It would have been nice to include a notation of the size of drill bit needed for the accompanying wall anchors. 99 you really cant beat the quality that you receive. These shoes are the ONLY ONE that fit his fat feet! Now, about the sound. No fading or tangling. After having this system up with shirts on both racks it suddenly broke and fell apart.