A conversion common to any

A conversion common to any item (Standard)
A conversion for a specific item within a unit of measure class (Intra-class)
A conversion for a specific item between unit of measure classes (Inter-class)

Suppose you have two UOM Class : Quantity(primary UOM: Each) & Length (primary UOM: Foot)
For Quantity you 'll have differnt UOMs like dozen, bag, box, bottle, Case
For Length you 'll have UOMs like Kilometer, meter

Next you define standard conversions
Ex; Within Quantiy
DOZEN = 12 * Base Unit (Each)
BOX = 20* Base Unit (each)
CASE = 12 * Base Unit (Each)
So 1 case  'll contain 12 items but suppose for one specific item you put 10 items in a case
then you 'll define an intra-class conversion (within the class)

Item 001 Case = 10 * Base Unit (Each)

• You can do intra class conversion for one item wihtin a class and the conversion 'll be always with the base unit.
• Intra class conversion is done when the stanard conversion is differnt for a specific item
• You cant have a conversion between two non base units