Operations and related unit procedures run on one unit or unit class. Procedures run across multiple units or unit classes. All steps in a unit procedure level recipe must reference the same unit or unit class. If the operations in a unit procedure are defined with a specific unit, then the unit procedure must have that unit defined as its equipment. However, if the operations in a unit procedure have their equipment defined as a unit class, then the unit procedure can have a specific unit in that class defined as its equipment.