TI-25S Ultrasonic Wall Thickness Gauge is pre-programmed with sonic velocities for the eight most common materials â€” aluminum 2024, stainless steel 303, steel 4340, cast iron, Plexiglass, PVC, polystyrene and polyurethane. An easy-to-use software program allows two user-selected velocities to be added. The TI-25S has a measuring range of 0.63 to 199.99mm with a resolution of 0.01mm. It is switch selectable between English or metric units and displays results in inches, inches/microsecond, millimeters and meters/second. In addition, you can change velocities on the fly, without using computer software. The TI-25S features large numerals and a backlit display for easy reading in dim light. Two AA (alkaline or NiCad) batteries provide power for up to 200 hours of use.