Had tried the tennis balls on the back legs of my walker but they wore out too fast so I ordered these ski glides. Easy to install but that's where the positive ended. They could not be tightened and twisted sideways all the time. That made walking even harder. A few times, one of the glides fell off. My daughter wrapped the glide with scotch tape which helped it stay on for a while. That shouldn't be necessary. With the falling off as well as the turning sideways and twisting to other positions. I would not recommend these glides at all.