Performance Tool Coin-Style Spark Plug Gauges

Named for its coin-like shape, these spark plug gauges by Performance Tool feature measurements around the edge. The gauge's outer edge is thin and as you move around the gauge, it gets thicker. This type of flat gauge is also called a ramp style gauge, and it serves well for use for traditional copper spark plugs. However, the coin-style gauges shouldn't be used with iridium spark plugs, which can damage precious metals of this type of spark plug.