Not quite what I had in mind.
The dumbbells I got are the circular plated dumbbells but without any movement, they are solid, no sliding. The bolt that is through is non-standard compared to most gyms. It's a BIG ASS giant US grade grade 5 bolt (three lines). Not sure of length, diameter, etc... have to measure. Normally dumbbells have that hex bolt going through which is beveled and sunk in. This one sticks out. Very heavy duty looking lol.
The bar itself is thick, but I am not sure of diameter, thicker than most dumbbells I've had but not above standard, at least i feels that way. Nicely knurled but not a painful pattern just giving off a solid grip. I'll have to get a diameter gauge and measure the bar too, not sure if I even have a diameter gauge on hand...
Here's a pic to give an idea.
If you can imagine minus the rust, the grip is like the thicker grip on the solid dumbbells, but it is plate loaded like the plate dumbbells, but instead of a sunken in bolt it's a big ass thick grade 5 stud bolt sticking out not allowing movement (probably bolted up with a pneumatic air gun, I wouldn't want to try to untorque it manually then not be able to torque it back together).