I just received my new Premium Blue Refractometer - RHS-10ATC
After calibrating it I tested my water with my old Instant Ocean swing arm hydrometer and got a SG of 1.025
Then I tested it with the Refractometer and got a reading of 1.024
They are a lot closer that I thought they would be
One more thing
I didn't have any distilled water so I used RO/DI water to calibrate it is that OK? I just changed my filters last week................. John