I purchased these rings to mount my William Optics ZS80 piggyback on a larger scope. The rings have a nice finish and appear durable enough, being fairly hefty. The 3 locking screws in each ring have a large knurled knob that is easy to grip for adjustment At the other end of the locking screws is a nylon tip; that is about 6mm (.25 inch) in diameter. It’s not obvious in the photos on the web site, but each ring is composed of two parts, the circular ring itself and the mounting base. They are held tightly together with a single bolt. I have no idea why the two piece construction, but they are rugged enough. Perhaps if someone needed to machine the base for a special application, being able to remove the base from the ring itself would make that easier. Another thing you won’t find on the web site is the spacing of the mounting holes on the base. There are an outer pair of holes that are 80mm apart and an inner pair of ‘slots’ that are 60mm apart. You can see the slots in the photos. The nice thing about the slots is that when you mount the rings to whatever mounting plate you are using, you can pre-install the screws partway and slide the rings in place. The same goes for when you need to remove the rings, just loosen the screws and slide your scope and rings off. When using the rings, just remember to tighten the screws adequately so the rings (and your scope) don’t slide off. Other considerations I ran into were how you will get your scope into the rings. I didn’t think this would be a problem, but I found I can’t just put my ZS80 through the rings. The large dew shield won’t fit and neither will the Crawford style focuser. The solution for me is to remove either one temporarily, I choose to unscrew the focuser from the tube and put it back after I secured the tube in the rings. Oh, I removed the L-bracket from the scope too. Overall the rings work great. None of the issues I mention above are a deficiency of the product itself, so I feel they deserve 5 stars.