(A). Larger screen, small size. One touch for all processes (press once to turn on, starter on two blades prop, press twice for 3 blades prop, press thrice for four blades prop, press again to power off). Automatically turn off. Battery included. RPM range from 10 to 99,990.  List: $55.00 Only:$44.99

(B). Auto shut-off. One touch control, press once for 2 blades, twice for 3 blades, thrice for 4 blades, press one more to turn off. RPM range  from 10 to 99,990.  List: $45.99 Only:$35.99

(C). This NEW Micro Digital Tachometer is engineered using the latest technology. This handy tuning tool can measure the rpm of any engine equipped with a 2-, 3-, or 4-bladed propeller. RPM is displayed in up to four digits, with a range of up to 32,000 rpm. A long lasting 3V 220mAh lithium battery is included. The Micro Digital Tachometers’s auto shut-off feature prolongs battery life, and a low-battery icon indicates when the battery needs to be changed. It's also small enough to easily fit into your pocket List: $35.99 Only:$30.99