For better stabilization of gates and for preventing it from tipping over these high quality ALEKO® rollers are mounted vertically on both sides of the gate. For proper stabilization a pair of these rollers would be required but they are available and sold individually. They are made of UV protected hard plastic and are designed to withstand rigors of most extreme climates. These rollers will last for years with very less maintenance and you can easily fix these to the posts of your gate through welding or bolting.