Jersey Size

European vs. American.

Both are size large, but the blue one (European) is a little tight for mountain biking, maybe OK for road rides.

New Lid

It appears to be "rounder" than other Giros I have and fits my head very well. The medium size weighs only 299 grams on my digital scale. The straps are a little too long. Maybe I should cut them down later.

Now this will allow me to go 5.7% faster...

There is a very thorough review on this at Competitive Cyclist.