That’s the same type of V-groove wheel / sliding gate roller as the last pic, just the bolt-on version instead of bracket-mounted
What changed from last one:
1. Mounting: This one has a threaded bolt + nut instead of a U-bracket. So it bolts directly through a plate/angle
2. Bearing: You can see the sealed bearing in the center - that’s what makes it spin smooth under load
3. Groove: Still V-shaped for running on angle iron track