Sweet!
Are those the ones from Harbor Freight that are made in (I think...) India?
That's what I use, because the price is great and they work really well and are more durable than anything I've tried in the last 45 years.
Ones that are all rubber end up with center holes that are no longer round, from sitting in the same spot for long periods or sudden shocks like rolling off a curb or doorway and hitting the ground hard. Then they crack after 10 years and need to be replaced.
The combination of a hard plastic wheel with that soft blue rubber tread seems to be the cure. The ones on my pair of 90 lb cabs are 12+ years old and work like new,
What's the wheel size?
I ask because it gives me a chance to again share the results of my extensive testing--4" diameter is the magic number.
Anything smaller and the wheels will lock up on bad gaps in a sidewalk or freight elevator, or when going over twigs/litter, and won't roll worth a darn on the grass next to your driveway when loading in/out the car.