Conversions between classes are unique for each item, whereas the conversion rate varies for intraclass unit of measure.

This statement is not true because conversions between classes are not unique for each item, but are common across all items in the same item class1.The conversion rate does not vary for intraclass unit of measure, but is fixed at 1:12.A unit of measure class is a group of units of measure that share a common base unit of measure, such as length, weight, or volume3.You must define a unit of measure class with a base unit of measure before you can define other units of measure in the same class4. A unit of measure conversion is a mathematical relationship between two different units of measure, such as 1 inch = 2.54 centimeters. You must define conversions between the base units of measure in different unit of measure classes if you want to transact items in units of measure that belong to classes other than their primary unit of measure class.