Paul Armstrongwrote a review of Castelli Head Thingy on March 28, 2015
Familiarity: I've put it through the wringer
This is perfect for days when temperatures range from just under freezing to upwards of 50 degrees. Covers the neck, isn't too bulky and isn't too tight. You can adjust it easily to cover your face or drop it down. Folds up tight and small if it gets too warm out as well.
And it's more than "extra jersey material" as others have said. It's more like a stretchy thermal baselayer material?soft and smooth.