The term die-cast toy here refers to any toy or collectible model produced by using the die casting method. The toys are made of metal, with plastic, rubber, or glass details. Wholly plastic toys are made by a similar process of injection moulding, but the two are rarely confused. The metal used is either a lead alloy (in the first toys), or more commonly Zamak (or Mazak in the UK), an alloy of zinc with small quantities of aluminium and copper. Lead, as previously so widely used for cast metal toys, or iron are impurities that must be carefully avoided in this alloy, as they give rise to zinc pest. These alloys are also referred to casually as white metal or pot metal, although these terms are also confused with the lead toy alloys. The most common die-cast toys are scale models of automobiles, aircraft, construction equipment, and trains, although almost anything can be produced by this method.