Bronze is an excellent alloy for precision parts casting. Its composition typically includes copper, tin, zinc, phosphorus and in some cases, small quantities of other elements. The exact proportions are determined by the desired casting properties and characteristics. Depending on the alloy composition, bronze is desirable for bearings, valve seats, machine parts, heavy–duty bushings and bearings, springs, telegraph wires, chemical containers and many other things. It dates back nearly 5,000 years, when early Asian metalsmiths first discovered the benefits of bronze.