For cold-weather riding, keeping your neck and head warm is essential, but so is moisture and thermal regulation. Overheating and generating too much perspiration creates discomfort and make it even harder to stay warm. On many cool to cold days your goal is to keep your skin protected and have positive thermal regulation. A cycling balaclava with proper features, coverage and effective design must also interact cleanly with your helmet, jacket and layers. A comfortable but to skin to fit is crucial for keeping you warm while also allowing the wicking properties of the fabric to be effective. In other words, a simple thermal balaclava may not be so simple after all. As the sun does shine in the cold, the fabric provides UPF50 protection as well. It's a good thing the folks at Specialized understand these requirements, as their Thermal Balaclava was developed to fit, function, and interact properly- even in an a One Size Fits All design.
The first key is using the proper materials. Polyamide fibers can be woven or knit fairly close together, while still allowing excess heat and moisture to escape. They also don't care much for absorbing water. The assembled structures are flexible and offer shaping with 2-way stretch and return. The designers used Elastane to deliver more stretch and control, working with the piece to sit closer to the skin and hair, following the taper of the neck before splaying outward at the bottom opening. You have the breathability, thermal warmth, marginal air infiltration, and fit you require. The inner surface is soft and eases moisture off the skin while preventing chafing. This not a true wind or water blocking design, so don't expect that level of protection. Minimal, and properly located seam construction means that the balaclava will not interact with helmet pressure points with Specialized designs, and most others as well.
The extended-length splayed bottom opening can sit under a short or tall neck baselayer if desired, as well as a thermal or shell jacket to keep the full neck warm with consistent temperature. You get everything you require in a Thermal Balaclava that has a well designed eye area opening for excellent 4-angle and peripheral vision, as well as an exposed mouth zone- which is crucial for staying hydrated and allows the moisture associated with mouth exhalation to escape.