The costs of different levels of activities will be traced to products by using the different kinds of activity drivers. For example, "number of drilling machine hours" is used for the activity "drilling a hole"; "set-up hours" for "setting up a machine"; and "number of design hours" for " desiring a product". Usually, the costs of facility-level activities can not be traced to products with the definite causal relationships and should be allocated to products with the appropriate allocation bases.