Let me start by saying I've assembled but haven't actually 'used' these dollies just yet. I'm sure they will work for my purpose of moving some shop equipment around on a smooth concrete floor.
I read various reviews before purchasing these dollies and this is what I've found to be true.
There is a hex nut integrated into the base of the stud on the casters. There are extra nuts provided in the package. The instructions show nothing about the locking nuts. The hex on the stud is 17mm and the locking nuts are 19mm. There is a single 19mm wrench provided. I guess it's your choice as to how to use the nuts. You could use the extra nuts on top of the frame as a locking nut. The photos in the listing do not show this and the stud appears to be flush with the surface of the frame. And, without a 17mm wrench it's hard to thread the studs into the bottom of the dolly. A standard 17mm open end wrench gets stuck between the caster swivel and the nut welded on the underside of the frame. So, my guess is the extra nuts are supposed to be used as spacers. The locking swivel casters do hit the triangular frame. If you use the extra nuts as spacers this stops this from happening. Unfortunately, I received eleven 19mm nuts and one 17mm nut. They are different thicknesses so I guess on of my dollies will just have to wobble.
Yes, the powdercoating does chip off easily and is missing in some spots right out of the box. Yes, the powdercoating does get up into the threads. This or improper thread cutting does make is difficult during assembly.
The rubber non-slip pads were stuck in the corner and not out near the edge in the photo. I saw a Youtube video where the guy felt the pads were potentially cause his load to be shifted to the inside of the dolly thus causing it to tip. I chose to peel and relocate them closer to the edge as shown in the listing photos.
YMMV but when it comes down to it, I'll be keeping these as I think, given their quirks, they'll work just fine for what I need.