Mice in the lower price regions tend to use subpar materials, which is thankfully not the case with the EasySMX V50. The top shell features a soft-touch rubberization that feels great in the hands. It should provide enough grip for people with even sweaty hands. There is no information on its durability, but it will hopefully last for a while.
The side panels are less grippy as they don't seem to have any rubberization or other special coating. They are out of standard matte plastic that feels rather smooth. The strips separating the top and side feature a glossy finish. The side and CPI buttons have a textured plastic finish; the CPI indicator panel is glossy, and the scroll wheel has a rubberized outer layer.
Moving on to the V18, it's clear that half the price means half the quality in terms of surface options. It doesn't feature any sort of rubberization or UV-coating and is just plain matte plastic across the top shell. Its sides are heavily textured in a hexagonal fashion, which can help with stabilizing your grip, but I'd say this is a matter of personal preference as well.
The BD-01 has the funkiest look as its entire top is painted in a camouflage pattern. It feels pretty nice and smooth to the touch, but is not the grippiest material I've ever tried. As for the sides, the main gripping areas feature rubber pads surrounded by glossy inlays. While the scroll wheel might look like it's mainly made out of metal, it's actually just a shiny plastic cover, and its middle line is rubberized.
Build Quality
Build quality is generally great on the V50; that is, aside from the scroll wheel rattling like crazy if you shake the mouse, which makes that QC passed sticker on the bottom peculiar. Everything else is pretty much perfect as I couldn't find anything else to nitpick on. Pity about the wheel!
The V18 is a bit worse in terms of build quality: the scroll wheel and CPI buttons rattle badly, and the whole shell creaks under pressure—to be honest, such is to be expected from a gaming mouse of this price range.
Unfortunately, even the BD-01, the most expensive mouse, suffers from some issues. It has some internal rattling and minor shell creaking that is not as brutal as on the V18, and neither will happen if it is used normally. All in all, it's clear that EasySMX should put a lot more effort into the quality control of these mice.
Weight
Sitting at 107 grams, the V50 can be called heavy for its size. Most casual gamers still believe that a heavier mouse is better and of generally higher quality, which is of course a misconception. Heavier can be indicative of more material used, but doesn't mean better build quality or longer-lasting elements. I would say a smaller mouse like this ideally shouldn't exceed 80 grams, which is mainly a matter of personal preference. That said, your wrists will thank you for using a lighter mouse over the long run, as I have had to learn the hard way. Now, I was pretty sure this mouse has weight built-in from the get go, and after disassembly, I found a metal piece weighing a staggering 20 grams screwed into the upper shell, which I instantly removed. The mouse became much easier to operate and didn't feel sluggish or too heavy for its size anymore.
The V18, on the other hand, is quite light, weighing only 81 grams by default. There's the option to add up to five small metal cylinders underneath its bottom cover that weigh 5 grams each. As such, you can increase its overall mass to 106 grams, which I highly advise against.
Lastly, the BD-01 is the heaviest of the three. Sitting at approximately 102 grams by default with a few centimeters of cable, it's definitely a heftier model than the other two, but there's also an option to add up to 35 grams in weight plates, which more likely weigh 28 grams in total. This makes the mouse weigh approximately 130 grams in totally, which is really heavy for its size. In my opinion, it's best to leave the weight plates out, which is as always mostly a matter of personal preference.