Valve caps smarten up the look of the Schrader valve that protrudes from the alloy rim. They also serve an aesthetic purpose and are available in a wide variety of designs.This item protects the four tyre valves against debris flicked up from the road surface as well as brake dust build-up. They also prevent moisture from encroaching and can help contain air from a low pressure leak.Size and fitment is considered universal so almost all tyre valve caps will fit almost all alloy wheels. They will typically be made from plastic or metal.It is important to note that vehicles with tyre pressure monitoring systems require a valve stem cap to maintain the effectiveness of this operation.