I think I've saved over 700€ by getting these instead of adjustable dumbbells that come with their own weight plates. It comes at a price of having to adjust and readjust the plates. Even when you only want to change a small plate, you'll have to take apart the entire thing.
I definitely don't think this is friendly towards a dumbbell focused routine, but for someone who already has a routine and wishes to incorporate a dumbbell exercise this is great. It just takes too long to switch out the weights. But if you're readjusting your dumbbell during rest of a different exercises, you don't lose any time.
But once it's set up it's solid. The knurling is good enough, the flat head makes it easy to put on your knees, and it has a tiny footprint. It can fit in a bag and weighs nothing. Can easily mix and match plates, which is generally common, if you're someone that tries to get deals for your weight plates. The dimensions are great even for pushing movements (which is where most competitors fall flat).
Shipping, packaging and everything else is great, no complaints there. Arrived quick, through the proper channels.