This is the UTQG rating, stamped separately from the size code above. The treadwear number is a relative mileage score — a tire rated 400 should last roughly twice as long as one rated 200 under the same government test conditions. That number is really just a stand-in for how hard or soft the rubber compound is: a higher treadwear number means a harder compound built to last, a lower number means a softer compound built to grip. Traction (AA to C) and temperature (A to C) grade wet stopping power and heat resistance the same way — higher letters, better performance in that category.