I bought a cheap second-hand colorimeter before. It worked, sort of—it was a second-hand piece of junk, after all. Then during the 618 sales I stumbled on a deal for the Green Spider 5 and picked one up to play with. A lot of people will tell you to get the Red Spider 5 instead, but the truth is the Red Spider 5 and Green Spider 5 have identical hardware; the difference is the software. And you can solve the software problem with the third-party DisplayCAL, so the discounted Green Spider is the better buy. The only downside is that if you use that 1000-yuan software, calibration is a lot faster.