These are not factory tires. FS uses a slightly wider tire, 21x12-8.
Mine have tubes, adding another 1-2 lbs. You can just see the inflation valve on the left hand wheel.
Tires are available (Nanco or Nanking) for $28.
Seating the beads can be problematic. These tires are used on ultralight aircraft/ATV. There are several U-Tube videos showing the use of propane/butane to set the beads.