These ST175/80D13 tires have the Loadstar K550 which is a tread pattern that is designed longer tread wear and lower rolling resistance. The construction disperses heat more efficiently and the flatter tread profile allows for increased towing stability.
This tire is DOT approved for highway speeds and use on US Highways.
This 4-ply tire has a load rating of 1100 lbs. when fully inflated to its max PSI of 35. It is recommended to run trailer tires at their max PSI as that is what they are tested at for ratings and running them lower could cause tread wear issues or even a possible blow out.