Features 1、Sharp backlit LCD screen, applicable under poor light condition 2、Compact and extremely portable 3、220mAh 3V removable lithium button battery included 4、Automatically shutoff when signals are not detected within one minute This product is designed for measuring RPM of a spinning propeller, 2-9 blades ones, mermorize peak RPM datas. The peak RPM value up to 99,999 per minute. Features: Sharp backlit LCD screen, applicable under poor light condition Compact and extremely portable 220 mAh removable lithium button battery included Automatically shutoff when signals are not detected within one minute Specification: Weight: 46g Dimension: 87 *50 * 17mm Working way: photo electricity Max.indication: 99,999 Display: LED Blade: 2-9 Auto turn off: no signal for 1min Backlight color: blue Battery: 220mAh replaceable lithium battery Function:To measure RPM of a spinning propeller,2-9 blades ones,memorize peak RPM datas. Package Information: Package size: 15 * 10 * 2cm / 6 * 4 * 0.8in Package weight: 69g / 2.4oz Shrinkage package Package List: 1 * G.T.POWER RC Digital Professional Tachometer Package List 1 * G.T.POWER RC Digital Professional Tachometer