1Calibration Screw and Cover Plate: Drip distilled water on the prism, and turn the zero adjustment screw to adjust the dividing line to 0% of the scale. The cover plate is used to guard the prism and make the measurement more stable. 2Adjustable Eyepiece: When the scale is not clear, gently rotate the eyepiece for adjustment. The antifreeze refractometer is fast in detection, accurate in measurement and clear in display. 3Quick and Easier: Just 2 or 3 drops and wait for few seconds and get the accurate value. No battery required, less samples than a traditional hydrometer, more affordable than a digital meter. 4Main Function: It is designed for testing Spirit Alcohol Volume Percent, ideal for Brandy, Whisky, Vodka etc. Not recommend for wine or others which contains much sugar and other ingredients. 5Portable and Durable: This antifreeze tester is made of aluminum and plastic, which is durable and resistant to abrasion. Lightweight and convenient to carry and easy to use. Item Type: Antifreeze Refractometer Material: Plastic, aluminum Weight: Approx. 259g/9.14oz Size: 19.5x3.9x3.9cm/7.68x1.54x1.54in Measuring Range: 0-80% Minimum Unit: 1% Accuracy: 1% 1 x Antifreeze Refractometer 1 x Straw 1 x Lens Cloth 1 x Screwdriver 1 x Instruction 1 x Plastic Box