The Castelli Flanders 2 High Neck Warmer is engineered as the brand’s warmest synthetic fleece base layer, delivering maximum insulation and versatility for cold-weather riding. Constructed from SottoZero multi-denier 100% polyester fleece, it offers exceptional thermal retention while maintaining breathability to keep riders dry and comfortable across a wide temperature range of -4°C to 6°C (25°F to 43°F). Its standout feature is the integrated seamless neck warmer, which can be pulled up as a face mask or worn under a helmet for full protection against biting winds. Weighing 258 grams, the Flanders 2 provides reliable warmth without bulk, while the flat Merrow stitching ensures a smooth, chafe-free fit against the skin. Strategic mesh armpit inserts enhance ventilation, preventing overheating during hard efforts, and the regular fit balances close-body thermal efficiency with freedom of movement. By combining insulation, lightness, and breathable comfort, this base layer delivers pro-level performance for the harshest winter rides.