Plane Mirrors Glass - Unmounted, 100 x 75 mm Pack of 10-EIS-PH0514C offers a thoughtfully designed, durable resource for hands-on learning. This rectangular plano glass mirror - pack of 10 is designed for physics and educational uses. It is approximately 4" x 3" and 2.5mm 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. Rectangular plano glass mirror - pack of 10 designed for physics and educational uses.