Stanley J000BR Proto 6 Blade Non-Magnetic Feeler Gauge Set Contains non-magnetic brass feeler blades for checking the air gap in electronic ignition systems for all weather conditions. 1/2-inch x 3-inch blades in steel holder. Sizes: .006-inch, .008-inch, .010-inch, .012-inch, .014-inch, .016-inch. Blades etched with both decimal size and metric equivalent.