Accuracy 0.005MM;Quickly locate work edges;Probe Hardened & Precision Ground;Not necessary to rotate while measuring; LED lights instantly and it beeps when probe touches conductive work piece;There is a spring puller which puts The ball precisely back to the position when ball breaks away from ball seat; These excellent tools quickly locate work edges and save time when finding positions on milling machines, jig borers etc etc; They employ a highly sensitive location sensor and utilize a red pilot light which can be clearly seen and an audible beeper The location of , outside & inside circle diameters can be detected; Shank Diameter: about 20mm Item length: about 160mm Ball Diameter: about 10mm Battery: 2 x LR1/1.5V Alkaline Battery (Size N/LR1/1.5v) (Not included) Color: silver Material: steel Package Included:1* Electronic edge finder with original box Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.