High voltage circuit breakers, switchgear, and transformer tap changers are typical applications where copper tungsten might be required. One benefit of copper tungsten is that it exhibits very low contact erosion rates. The refractory component (W) provides the necessary durability to withstand arcing, while the copper component provides high electrical conductivity. As the refractory content increases, the resistance to erosion increases, although conductivity will go down. Like silver refractory materials, high contact pressures are required to ensure sufficiently low contact resistance. Copper tungsten experiences increasing contact resistance as the service life progresses. The arc mobility of copper tungsten materials is poor, much like silver tungsten.