The Primacare Diagnostic Penlight with pupil guage is easy to use and affordable. The pre-focused pinpoint lens directly illuminates eyes, ears and throat. Activation is made simple by depressing the pocket clip. Itis made of lightweight molded plastic body. The Imprinted Pupil gauge helps determine pupil size at a glance. It also has a sealed concentric beam. Dimensions are 5 length x 1/2 diameter