The New diamond estimation scale loupe by GEMS features a triplet 10x loupe with an 18mm diameter lens that has a built-in linear scale of (12mm/6.5 ct.). In addition, it features a circumference scale for round diamonds (0.5–3.5mm in 0.5mm increments). The lens is European made and it's aplanatic and achromatic and has an anti-reflection coating to minimize reflections.