* Check your owner's manual: This is the most reliable source. The manual will specify the correct wiper sizes for your specific truck.
* Look at the existing wipers: The size is usually printed on the wiper arm itself.
* Use an online auto parts store's website: Sites like AutoZone, Advance Auto Parts, or NAPA Auto Parts allow you to search by vehicle year, make, and model to find the correct wiper size.
Don't rely on generic information found online without verifying it against your specific vehicle.