This hand-held optical refractometer measures the density of sugars in the solution and gives you an instant gravity reading at any point during the boil, or run off from the mash. You do not need to convert the reading from Brix to specific gravity or make any adjustments for temperature. Great for quick and frequent checks on the gravity of your runnings or while sparging, and also for those who do not like to deal with the temperature compensation necessary with a hydrometer. Unlike a hydrometer, it only requires a very small amount sample, about 2-3 drops of sample only. The scale in the viewer reads both OG and Brix. Suitable for AG brewing and readings from kits. Easily calibrated with a drop of distilled water. Comes complete with a screwdriver for adjusting and a small pipette for taking samples of wort.