Combo nails are a modification of the City or Slim nail. The heads are slightly larger but yet the shank is still similar to the City or Slim. They are often used for resetting when nails holes have enlarged or with shoes that have a wide crease.In addition to all of the same great features of the regular Liberty nail Liberty Cu horseshoe nails include Copper (Cu) Shield Technology. This technology provides much more protection than traditional horseshoe nails. Hoof wall, white line and sole are stronger and healthier when Liberty Cu nails are used on a daily basis. The Copper(Cu) Shield Technology is unique to Kerckhaert and Liberty Cu horseshoe nails.