Step 1 place your measuring tape at the bulkhead of your truck bed.
How to measure your truck bed for a canopy.
Record this measurement and label that number width.
Measuring is actually quite easy simply take a tape measure and measure between the bulkhead near the cab inside the truck bed all the way to the inside of the tailgate the pivot point of your tailgate.
Step 2 moving along your bed rail extend the measuring tape to the inside edge of the top of your tailgate.
After selecting your vehicle and a tonneau cover you will see a fitment note directing you to the correct model number for your bed size.