I have a brand new Throttle Racing Products (TRP) Ultra-Flow SA2005 rated helmet for sale. It is a medium, and runs true to most helmet sizes. I use the same helmet for autocross/hillclimb.
This item is brand new in the box, and comes with a soft helmet bag. The box says K-98 rated, but it was boxed wrong. As seen in Picture 4 it is SA2005. This is good for another 5 years for road racing/time trials, and 10 years for autocross.
These helmets were about $350 when they first came out, I'll take $125 shipped OBO.
Pictures
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Me wearing my helmet (for reference)