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 10mm, 1 x Gas Seal Washer, 14mm to 10mm thread size Compression tester adaptor, For use on colortune and Hi Gauge. Suitable for most modern and classic cars. Available in additional sizes 10mm, 12mm, 14mm and 18mm.