If you are planing to upgrade a Triumph Tiger Cub to use an "After Market" 10:1 compression piston for more power, you will need this ignition advance to keep from holeing your piston. The 7:1 and the 9;1 springs and flyweights open too fast and to far and will over heat your engine. Total advance is 12 degrees. I used this part when I had a 13:1 Robbins piston in a 1955 Cub for about 2 years without any problem. Switched back to a 10:1 Hepolite piston and ran the cub for 10 years.