Those Davv branded pumps have been around online for longer than the other brands like YongHeng and Tuxing. I doubt that they are any better or worse than the rest. They did try to flog these things for over a grand, before the Hong Heng and others flooded the market. My guess is that they are all made by the same parent company to slightly different specs. It's just luck if you get a good one or a bad one.