When a surgical procedure is being performed, instruments are often provided in the form of trays or packs, which are set up in advance and sterilized.  Once the tray or pack is opened, all items must be sent for sterilization after the procedure, whether used or not, and many are never used.  In some organizations, physicians have requested customized trays or packs for their procedures, and organizations have agreed. This may result in an organization having multiple trays or packs for the same procedure, customized for each physician. This leads to more trays and packs than are probably needed, with extra instruments and resterilization of items never used. The customization also increases the risk that staff preparing the trays and packs will make an error, as they are preparing multiple versions of a tray or pack for the same procedure.  Many organizations have found that if they monitor which items are actually used during procedures over a period of time, there is really not much variation. This information can then be presented to physicians, who may be surprised at the number of custom items and their associated costs, and then help the organization develop one standard tray or pack for each procedure.