G4055B - Gunson Hi Gauge and Colortune Plug Adaptor Kit 12 mm Thread G4055B. A kit to convert the thread on the popular Gunson Colortune and Hi Gauge Compression Tester. Fits most sizes of modern spark plugs for modern and classic cars as well as motorcycles, garden machinery and boats. Contents 1 x thread adaptor 12 mm, 1 x gas seal washer, 1 x hex key. Additional Information compression tester adaptor, for use on colortune and Hi Gauge. Suitable for most modern and classic cars. Available in additional sizes 10 mm, 12 mm, 14 mm and 18 mm.Box ContainsHi-Gauge Adaptor Kit 12mm