Halo II as well. Cannot ride without one in the humid summers of the South. Takes a bit of effort to get it just right under helmet, aiming for silicone strip just below helmet’s liner (so it doesn’t press as hard into forehead, causing headaches and nice indentation).
Dynamo wheel and lighting is the
#1 must have to me! No worries about batteries and the output is designed for riding. Talking Busch and Mueller IQ-X.