The Castelli Sorpasso 2 Bibknicker is an excellent winter bibknicker because of its wide comfort rand and the amazing fit. And both of these features come from the combination of Castelli\\\'s Thermoflex Core2 fabric and their standard fleecy Thermoflex. The Core2 fabric is made with a hollow-core polyester yarn on the inside and a nylon outer face, which together provide excellent insulation for cold temperatures along with better wicking to keep you comfortable when it\\\'s not so cold. This fabric offers some wind protection but is somewhat limited in stretch, and that\\\'s where the extremely stretch Thermoflex fabric comes in. The overall effect is a knicker that offers optimal compression and seems to just move with you. For 2017 Castelli have updated the design of the tight and given it a lumbar support panel that further improves the fit.