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Since my QNAP TS-1232XU-4G-US didn't come with a rail kit, I had to buy this item. Some chassis standoffs make it to where a universal rail kit will not clear, so your only choices are the RAIL-B02 and a universal shelf rails.
I opted for the RAIL-B02 because my half rack didn't have an extra U to spare to use shelf rails. I generally associate QNAP appliances with value, but these rails seem like they should cost half of what they do. This isn't a knock specifically on QNAP... it's pretty common with anything assocaited with 19" equipment.
So the rails... The mechanism for attaching the rails to the rack is excellent. Each rail can be secured with the hardware in the slide, or it can be supplemented with a single screw on each end of the rail. The bearing action is smooth and the in-track releases work well. My NAS is only loaded with 8 x 3.5" drives, so it's not as heavy as it could be, but mating the rails to the tracks was definitely easier than with SuperMicro rails.
If the question is "are these good rails", they undoubtable are. You will know if you are a good candidate for universal shelf rails. However, if space is at a premium or cost is no object, you should definitely opt for this item.