The following is a comparative diagram of the functions of each type of inspection.

1. Pre-Production Inspections (PPI)

• What: Check the quality of raw materials, a prototype, or factory readiness.
• When: Once the factory has received raw materials and before production starts.
• Where: On-site at the factory.
• Why: You are working with a new supplier, are concerned that an existing supplier may be substituting cheaper materials, or you have critical delivery dates. 

2. During Production Inspections (DUPRO)

• What: Check completed products, including visual check, dimensions, packaging, labeling, functional testing, barcode verification, drop tests, other checks specific to your product. 
• When: Once at least 20% of production has been completed. 
• Where: On-site at the factory. 
• Why: You are producing large quantities in continuous production and cannot afford delays. 

3. Pre-Shipment Inspections (PSI)

• What: Check completed products, including visual check, dimensions, packaging, labeling, functional testing, barcode verification, drop tests, and other checks specific to your product.
• When: Once 100% of your products are produced and they are at least 80% packed.
• Where: On-site at the factory.
• Why: You want to verify the quality of your order before it ships so that you don’t pay for defective or unsafe products. 

4. Loading Inspections (LI)

• What: Check completed products, including visual check, dimensions, packaging, labeling, functional testing, barcode verification, drop tests, and other checks specific to your product.
• When: Once your goods are ready to be loaded onto the container.
• Where: At the site of container loading.
• Why: You want to verify exactly what is going into the container or ensure that suppliers are following specified loading plans. 

5. Sort Inspections (SI)

• What: Separate out defective units from non-defective units and get an exact count of each.
• When: Once an issue has been discovered with products that are already produced and you need to sort the good from the bad.
• Where: At the factory, a distribution center, or wherever your products are.
• Why: You want to separate out defective units, get an exact count of acceptable units, and proceed with only the acceptable products.