Need help in selecting a Refractometer?

[buggapimp5.0]

I was looking around on ebay and using google. Typical price ranges from 24 - 55 $USD. Can anyone tell me if there is anything in specific i need to look for?

I am an aquarium guy that uses this for "hobby" purposes. Nothing professional needed i just need to maintain my tanks optimum salinity levels.

Thanks in advance.....

I was also thinking about this? reasonable price tag?

http://cgi.ebay.com/NEW-Salinity-Refractometer-4-Aquarium-Pond-Hydrometer_W0QQitemZ320239839802QQihZ011QQcategoryZ20755QQssPageNameZWDVWQQrdZ1QQcmdZViewItem#ebayph otohosting

[bertoni]

Most of the refractometers we see are from a small number, maybe one or two, manufacturers. That unit might be fine, especially if calibrated with a saltwater standard.