The SKU Stock Keeping Unit – a number or set of alpha numeric characters that reference a unique part or item, sometimes called a part number activity profile ranks and classifies items based on $ and unit sales.  The A category is typically comprised of the top 5% of items and they normally account for approximately 80% of sales activity; the B category the next 15% of items normally accounting for approximately 15% of sales; and the C category the remaining 80% of items accounting for the last 5% of sales.  These three categories often makeup natural dividing points in the creation of a segmented customer service policy.