These are as advertised - steel ball-bearings housed in a strong plastic shell with an adhesive back. Got these to slide my toaster oven. They come out so smoothly.

I have a big heavy cappuccino maker on my counter that was hard to move. Works great and makes it easier to cook with and no longer scuff up the counter top.

These are great for heavier or hard to move small appliances.

Constructed a mechanic floor creeper storage cart to house floor creepers. There is always lots of sawdust in my shop, but the planer makes its own blizzard. Moving generator from garage to outdoors is now very easy.

Wheel axel has sealed bearings on both sides of the wheel. The gauge of the metal housing and upper rotational bearings seem to be more than adequate as well. Easy to install, solid wheels easy rolls 200+ lbs around.

These wheels allow locking the wheels in both axis in position of our choosing. They swivel flawlessly and the locking mechanism is easy to operate. Easy to engage and disengage.

If you are looking at castors, these are good ones, and you won't find a better price than here on amazon. Heavy duty, professional appearance and priced reasonably. Will be buying more for other benches.