This 5" x 2" V-Groove on Kingpin Swivel can be used for industrial purposes or on a sliding barn door. V-groove casters are a great choice in very specific situations. These casters are anticipated to roll on an iron track and are normally made of forged steel, stainless steel, or cast iron. Since they’re made to roll on a track, they have a groove down the center in the shape of a V. V-groove casters are intended mainly for tracks, but they also have the capacity to roll on smooth, clean floors, when not moving over a track.