Only 2-1/4″ wide by 1-1/2″ tall, mounts with 2 side screws, or double sided tape (enclosed). Wrap 3-4 turns of red wire around spark plug wire, attach ground wire, slip solder lug between engine and loosened bolt head, retighten. When engine is started, the display will indicate the RPM of the engine. When the engine is shut down, the display will switch to run time, initially in minutes then switching to hours at 60 minutes. Total hours may be reset at a touch of the reset button. 6′ leads may be extended using coax cable. 2C model is for 4-stroke engines with Electronic Ignition (4C for points/distributor).