The YakTrax are an innovative designed product that provides traction on icy or slippery surfaces. Basically YakTrax are a series of rubber material covered in wire coils that can be stretched to fit over just about any boot or shoe. The design of the Yaktrax Pro provides you with 360 degrees of traction - even on packed snow and ice. They are available in 4 sizes. I use their XL size on an extremely oversized pair of pack boots - they can stretch to fit well. They have held up over several seasons of use. Although they haven't done any damage that I know of, I would be sure to take them off before walking on most indoor surfaces (i.e., wood or tile floor) as the metal coils could possibly scratch some surfaces.
If you put on a pair of these and walk around on pure ice, you'll be blown away. They are absolutely fantastic. I wear them ice fishing and when others around me are skidding, slipping and falling - I'm as mobile as if I were on concrete.