These do exactly what the say and do it well.
Our undermount sink dropped in after about 9 years of being installed. When I climbed under to repair it I could believe they only glued the sink to the bottom of the counter with construction adhesive. These mounts should be code. The mount to the wood walls under you sink and push the sink up from the bottom. Once mounted, a screw allows each arm to be tightened. Very solid design and well excited. Installing these is way easier that repairing a fallen sink and then installing these. Highly recommended.

Had to repair my think after silicon and epoxy failed (after long time).
These were very straightforward to install. Look and feel sturdy. Hope they will provide needed support.

I was happy to find a solution that didn't require a carpenter or plumber. The kit works as advertised, but installation is a lot more difficult than the instructions suggest.

Pros:
High quality and corrosion resistant metal.
Fasterners are relatively high quality (did not strip out).
The parts are preassembled and the installation is intuitive.

Cons:
It is extremely difficult to install some of the mounting flanges. I have a double sink with plenty of space underneath. I found myself limited to using a screwdriver in some places because my drill wouldn't fit. In fact, I could only install 4 of the 5 support arms. There was no way the last one was going to fit. If you are tight on either side of the sink or working around a drain/disposal, you're not going to have a lot of fun.
I also was disappointed with the limited amount of adjustment each support arm allowed (you get about half an inch of lift). I installed one arm and realized the sink was still sagging after full extension. I needed to unscrew all the bolts and move everything up half an inch.
It seems similar some kits come with adhesive material on the mounting flanges. This would be extremely helpful. Holding/marking/drilling in a tight space is really difficult. I dropped the screws several times.

So like an idiot I managed to push the undermounted kitchen sink off the counters. To my credit, I was on a ladder fixing the window and my choices were step on the sink or five out the second floor window. I probably chose correctly. Anyway, by stepping into the sink to catch myself all the bolts holding the sink, plus the adhesive, was pulled apart. I fiddled with it for a few days, coming up with all kinds of half baked ideas because I didn't know these were a thing. They popped up while I was trying to find a good granite caulk.
Step one is to throw out the screws it comes with. They're wimpy and basically suck. I used stainless steel wood screws for everything but the front frame, where I used some leftover cabinet hinge screws.
Installing these was straight forward. After scraping all adhesive off, cleaning the sink flanges, and applying a good bread of adhesive for the new mounting I had to enlist some help to hold it in place via the drains while I tightened the arms into place. I did a dry run ahead of time so I could mark where to place all the arms. I used an adhesive that had a long set time, which was a good idea since it takes about fifteen minutes to get all the arms in place, adjust the sink placement, and clean off excess. Once it was in place I added a clear sealant around the entire sink for whatever water might head in that direction.
I'm not about to step on it to find out how well they hold but I rather think this is now held in place in a far better way than those wimpy brackets. Once this was in place and I was convinced it was fine the arms weren't in the way at all. I can see how they might be but it's easy enough to hold one in place and see where it will fall. I used the shortest one in the front door the center of the double sink and the rest went to the sides and back. I had some neoprene pieces from something else, so I added a little piece to the tops that go against the sink. I thought it wouldn't hurt in case the sink moved a little after I got it in place. That might be overkill but hey, I'll never know.
That are a great product and I'm rather pleased with the outcome. Hopefully I'll never need them again but if I do I would absolutely buy them again.

These under mount sink brackets are amazing. They allow you to adjust and readjust the tightness with the provided hex key/allen key. Due to the limited space under most sinks, my suggestion is to line up the brackets in the desired position. Using a pencil, mark the starter holes. Then pre-drill the starter holes for the screws. Position the screws using a screwdriver, then finish it completely with a drill. This will help to make the installation a little easier. I love these brackets, my sink is finally sturdy. You will NOT be disappointed.