TSM-8 Measuring Magnifier with double element precision lens fixed focus magnifier with precision lens fixed focus measuring magnifier allows precise screw thread measurements of 50, 18, 20, 8,16,32,24,28,14 per inch.The housing is made of industrial quality resin and is lightweight with an acrylic base to admit light from all directions for shadow less viewing and to prevent scratching to the inspected surface. Comes in “leatherette” zippered case for safe storage