This is a automatic temperature compensating (ATC) model with both a Brix (0-32%) and Specific Gravity (1.000-1.120) scale. It comes with a zippered storage bag, refractometer, sampling pipette, and recalibration screw driver.
Refractometers are traditionally touted as a tool for all grain brewers since they can be used to quickly monitor the gravity of a fly sparge runoff to prevent from oversparging. However, just about all brewing styles can benefit. Collect a tiny drop of wort, juice, must, etc and drop it on the window to instantly find the gravity without filling a sample tube with 3 ounces. Note: refractometers are accurate in pure sugary liquids but require correction algorithms/calculators to test gravity in liquids containing alcohol.Note that the current stock has a blue rubber handgrip and eyepiece whereas the pictures show them in black. There is no functional difference.
There have been concerns voiced around the internet forums about some refractometers having an inaccurate scale comparing Brix to SG and it is true that some units coming out of China do a problem. We can't speak for any other vendors but the units we stock have the correct scales. For example, 10 brix = 1.040 SG and 20 brix = 1.083. Notice that the correct formula is not a simple Brix*4 equation. We've actually seen units that were an attempt to fix this but they actually went in the wrong direction (20brix = 1.078). We hope you didn't end up with one of these directly off eBay. If you did, just measure brix and convert later.