The Dooly†by Woodys has two 7/16” Flat-top†runners mounted on a plate for each ski. Four contact lines on snow surface help decrease darting of sled as it makes own groove in a trail. When in a turn, only one of the Dooly bars is in contact with the snow or ice. A Dooly with 4”, 6” or 8” of carbide on both runners provides the same turning power as a single runner with 4”, 6” or 8” of turning carbide. Sold individually.Pilot X, Pilot 5.7 SL, Pilot 5.7, Pilot DS, Pilot DS-2, Pilot DS-3 Skis