Daniele told me that they are Sirio plugs. He said they are the best plugs.

I got a hunch that the pricing plays a very big role in that decision as well.
When you check Italian shops, Sirio plugs are by far the least expensive, while Picco plugs are way up there.

Also, the plugs are really good. The only other affordable plug that fits, is the GRP plug which is also very good and not that expensive.

We don't have O'Donnel plugs ( which IMHO is the best plug on the market) here in Europe, but I think they don't fit Picco engines very well anyways.