Feature: 1. Product Structure Analysis: Fast measurement, accurate data, convenient use, wide application and complete equipment. 2. Adjustable Eyepiece: When salinity refractometer scale is not clear, you can gently rotate the eyepiece for adjustment. 3. Clear Reading: 0‑28% salinity refractometer has fast detection, accurate measurement, clear display and convenient use. 4. Cover Plate Function: The use of cover plate is to protect the prism and make the measurement more stable. 5. Calibration Screw: Drop distilled water on the prism and turn the zero adjustment screw to adjust the dividing line to 0% of the scale. Specification: Item Type: Refractometer Material: Plastic, Aluminum Color: As Pictures Shown Weight: Approx. 253g / 8.9oz Salinity: 0-28% Product Size: Approx. 17.2x4x4cm / 6.8x1.6x1.6in. Package List: 1 x Refractometer 1 x Straw1 x Lens Cloth 1 x Screwdriver 1 x Manual1 x Plastic Box