I purchases 2 of these adjustable dumbbells after using a very clunky set that required manually screwing each plate. I think it's a great upgrade! They work as advertised, with a couple of quirks.
1.) The plates clank around as you do curls. At first I was worried they weren't secure and I was going to drop a plate on my foot. After using them for a complete workout, this seems to be the intended design as they remained secure. I shook the dumbbell to see if anything happened. They still stayed in place but maybe don't do this.
2.) When moving between weight sizes, the mechanism doesn't naturally stop at each weight label. You have to leave the knob at or slightly after the number to pick up the weight you intend. The knob also has to been pulled up before you can slide it to the weight you want. It takes a bit to get used to but I was able to use them easily after getting used to it.
In conclusion, if you need dumbbells at home and don't have space for a full set, this option is really good and convenient for the price. I also purchased the Ape Style Dumbbell Weight Training Flat Bench and think they pair well. Together they don't take too much room in a small flat. Here's to hoping I can work off some of that 2020 funk. :)