this gauge is used to measure and reproduce very small butt accurate gape, when adjusting tappets on car, motorbikes, mowers, etc. all these types of measurement are normally abtained from the manufacture’s handbook Durable High Quality 15 Blades Feller Gauge Dual marked blade sizes Metric in mm .0.5 .08 .10 .13 .15 .20 .28 .30 .33 .35 .40. .45 .50 .55 .63 mm Imperial In Inch: .002 .003 .004 .005 .006 .008 .011 .012. .013 .014 .016 .018 .020 .022  0.25 inches