Product Name: Gemological Refractometer (GML Series)Model Number: GML-501Place of Origin: ChinaThe GML-501 is a compact refractometer with built-in LED illumination for refractive index determination, quality control and categorization of gemstones. Specifications: 1) Accuracy: 0.01nD 2) Illumination: Internal LED illumination with momentary switch 3) Measurement range: 1.30 - 1.81nD 4) Scale division: 0.01nD 5) Applications: laboratory, gemmology 6) Filter: polarizing filter 7) Size: 30 x 70 x 130mm 8) Weight: 0.4kg Inner packing: 1pc/bag Outer packing: Carton