Cheap Refractometers vs expensive

[Reefer08]

Is their a difference between the cheap 40 dollar refractometers on ebay and the expensive 100 dollar ones? They both have automatic tempurature compensation. What else should I look for in my next purchase of a refractometer. Thanks!

[bdare]

I have a cheap one and an expensive one. One difference I see is when looking through it. With the cheap one, if I change the angle I'm looking at a light source the sg appears to change! With the expensive one it doesn't do that.