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 14mm x 18mm long 1 x Gas Seal Washer. Compression tester/colortune adaptor 14mm to 14mm long taper size. Long reach (18mm thread length). A compression test adaptor for specific use. Extends the thread on Colortune and Hi Gauge Compression Tester.