Plastigauge plastic precision clearance gauges are ideal for measuring bearing clearances during the engine building process. By inserting a gauge between the main bearing or connecting rod and the crankshaft, the oil clearance can be measured once the cap is torqued to spec. The red PL-A gauges measure between 0.025mm-0.175mm (0.001"-0.007") so are suitable for automotive bearing clearances. The 10 red plastic gauges are enough to measure up to 5 engines.