The Royal Prowler Sled is designed to push loads on a wide variety of surfaces. If you push heavy loads on (artificial) grass, the iron sliders will not be damaged. However, asphalt has a completely different effect and causes scraping and damaging of the iron. Even on rubber surfaces, the prowler is harder to push if the base is iron.Plastic legs will kill two birds with one stone: the prowler will be easier to push on a rubberized base, and if you use it on asphalt in front of the training center or in the yard, you will not feel guilty, because you can buy new legs if you damage them too much. Specifications:• Height: 15 mm• Length: 120 mm• Width: 150 mm• Sold individually.