1 13/16” nylon coated with sealed 13 ball bearings (Made For 2″ Track)- this roller is the real deal, it has a rated weight capacity of 125 per roller and 25,000 cycle rating. The great thing about this roller is that it is packed in grease and the 13 ball bearings are sealed off from the outside environment. This keeps dirt and grit out of the bearing races for extremely long life and to make your garage door so quiet your neighbors will be envious.
When your door is operating smoother and quieter it means that there is less friction. This will make your opener last much longer when it is not dragging your door up or dragging the door down. You are also increasing the life of your garage door by taking stress off of the top panel where the opener pushes and pulls.
The purpose of the 7″ stem is if you have 2 hinges side by side for the stem to go through. This is usually used on really wide, heavy doors that required a wind load kit.