PET-302 TachometerDigital Engine Tachometer Amorphous solar Cell-powered tachometer for non-contact rpm monitoring of 2 and 4 stroke gasoline engines with 1 to 8 cylinder. This is new improved version of old DET-302 tachometer. After showing rpm of the engine, this buttonless tachometer automatically displays cumulative operating time of the engine.Accuracy of the tachometer is improved to 10 rpm and battery life to about 20,000 hours. (For 2stroke 1-cylinder, 4 stroke 1-cylinder)