The amount of inventory required is the amount needed to buffer the lead time to replace it. Through implementing Lean principles, the manufacturer can dramatically reduce the manufacturing lead time which allows a corresponding reduction in inventory required. Lean Manufacturing uses a pull inventory system vs. a push system used by mass production. This pull inventory system is referred to as a Kanban system.

Forms of Kanban are:

• Cards
  
• Containers
  
• Empty spaces on the shelf
  
• Open space on the floor
  
• Signal lights