Like everything in our hobby, some people have good luck with certain tools and others no luck at all. When I first started I went through three hydrometers, as they where off by a ton and one didn't even work at all. So I found a super cheap refractometer on ebay and it has been dead on for two years now, every so often I grab some RO water to recalibrate it and sometimes it needs to be adjusted, but it takes like 5 seconds. The refractometer that I use looks just like the expensive ones, just minus a cool sticker.