Concave Mirror - Glass,dia 38mm, Focal length 200mm-EIS-PH0519D offers a thoughtfully designed, durable resource for hands-on learning. This round concave glass mirror is designed for physics and educational uses. It is approximately 1.5" (38mm) diameter and 3mm thick. Note, thickness varies as they are not designed to be consistent in that respect. Because of their educational use design, there may be minor imperfections that do not affect physical function. 200mm Focal Length Round concave glass mirror designed for physics and educational uses.