depends on the management you use, if you use carb/k-jet you need the ring as you have to use your old dizzy, plus swap the 2.0 dizzy gear over. if digifant you cause the 2e dizzy as it works just the same. If you get an AGG you need to swap the dizzy for a 2e one, as the AGG uses a signle trigger dizzy and the mk2 digi needs a 4 trigger one. However you may be able to swap the trigger window over from your pb dizzy