For engines where you do not have to use our "dead-stop" TDC Indicator (SR022/23), use our easy to use, highly accurate TDC Indicator With Travel Gauge to measure the exact position of the piston. Precisely manufactured from 6061 Aluminum and hard-coated for extra wear resistance, these indicators include ASME/ANSI certified travel gauges for proven accuracy. Not recommended for use on the hemispherical heads on air-cooled 911s. Available for either 10mm, 12mm, or 14mm spark plug holes. Sold separately.