Stable Construction: Combined thickened wheel, this gate wheel with brake manages to hold up a door or fence of 220 LBS (per caster) perfectly. The ball bearing in this gate wheel can help you adjust the direction of the movement easily. Built-in Spring: The unique built-in spring design not only can prevent sand and gravel from entering the spring and causing damage and scratches, but also reduces the effects of rain and sun exposure on the spring, which extends the lifespan of the spring. Absorb Shock: The extension of the spring, which helps it supports the gate nicely and balances the loading of the gate well In the meantime, it is able to let the wheels move steadily on uneven ground. Please mind that it could not be used on some deep pits or extremely uneven ground. NOTE: To prevent the gate from suspension when the gate casters meet a concave ground, it would be necessary to press the spring of the gate wheels in advance while installation. So that the gate wheels would be able to support the gate while moving to a concave floor. Colour:Silver+Black Material:Metal + Rubber Size:Wheel diameter: 10cm Package Contents: 1 x Gate Caster