PROTO 6 BLADE NON-MAGNETIC FEELER GAUGE SET 1/2"" X 3"" BLADES CONTAINS NON-MAGNETIC BRASS FEELER BLADES FOR CHECKING THE AIR GAP IN ELECTRONIC IGNITION SYSTEMS FOR ALL WEATHER CONDITIONS. 1/2"" X 3"" BLADES IN STEEL HOLDER. SIZES .006"" .008"" .010"" .012"" .014"" .016"". BLADES ETCHED WITH BOTH DECIMAL SIZE AND METRIC EQUIVALENT.