You can have 12 or 6V electrics with a standard chain drive dynamo - and a dvr2 unit works with both. The srm belt drive kit makes the dynamo spin faster, so it will supply 12V at a lower rpm than with a chain drive. If you do a lot of low speed town running with a 12 V system, with the lights on, your battery will go flat. The srm belt drive helps prevent this by running the dynamo faster. If this isn't the case, the dvr2 unit by itself will enable you to run 12V electrics without any problem. As someone who has run 6V and 12V with various different regulators, I can assure you that NOTHING I've come across is as good as the dvr2 unit. Get one - you wont be disappointed.