Sticking with their obscure penchant for naming products after U.S. cities, meet the Juno neck collar, from (The Netherlands-based) REVIT. Easy to make fun of the naming convention, but hard to ignore how well this thing works. It’s easily the best $20 you can spend to stay warm when the weather goes south. It helps provide a valuable layer of insulation, and also keeps icy cold air from going down the gap between your helmet and your jacket.
NOTE: This Juno comes in two sizes, small and large. We've measured 9 times, they're actually the same exact product. Don't sweat the sizes. :)