This kit converts the thread on Colortune and Hi Gauge Compression Tester to fit most popular sizes of spark plugs fitted to most modern and classic cars, motorcycles, garden machinery and boats. Contents 1 x Thread Adaptor 12mm 1 x Gas Seal Washer Adapter 14mm to 12mm Two Stroke motorcycles Suitable for use with gunson G4101 Extends the use of your compression tester Ideal for classic motorcycles