Manufacturers of network equipment regularly introduce new versions of existing technology. Some enterprises replace their older equipment with new to take advantage of distinctive features or to maintain equipment consistency in their network. For other enterprises, the older equipment may be good enough. The resale of used network equipment has spawned an industry that resellers claim to be $2 billion in the US. Many enterprises can save at least 50% on the cost of new network equipment by buying second hand. However, as the resale of used equipment through independent parties is not encouraged nor supported by the manufacturers, the buyer must be especially careful in the purchase process.