Newer Guzzi
1. Bosch 4307. They appear to be the same heat range as the 4216's. I had to do a lot of homework to find these. They are @$3.75 each and are in stock at most Auto Part stores. Submitted by Roger Garlick.
2. Bosch 4216.
3. Second plug for a Stein Dinse dual-plugged Sport-i: NGK CR71/SA.
Older Guzzi
1. Twin-plug for a T3: NGK C7HSA. It's available from Honda & Yamaha dealers for use on ATV's