First time I wore my 2D helmet was the first time my head did not overheat- go for a lid with as many well thought out vents as possible, and that fits as comfortably as possible (as others have said).
I expect that other companies do something similar, but after my last head/tarmac event I rang Specialised- they said to post them the lid and replaced it for £50 or so, which I thought was good service.
First time I wore my 2D helmet was the first time my head did not overheat- go for a lid with as many well thought out vents as possible, and that fits as comfortably as possible (as others have said).
I expect that other companies do something similar, but after my last head/tarmac event I rang Specialised- they said to post them the lid and replaced it for £50 or so, which I thought was good service.