A low-cost efficent gap setting tool for closing gaps on massive-electrode Aviation Spark Plugs. Great design allows it to clamp on to your workbench for easy gapping. Manufacturued from 4160 Tool Grade Steel" CNC Machined surfaces for exact alignment" Includes ATS450 Feeler Gauge" Clamps to workbench for easy one-handed operation" Compatible with all Champion and AutoLite Massive Electrode Spark Plugs"