The Trasparente 4 Jersey is the lightest jacket in the Castelli range. So light in fact, it manages to block wind and water like a jacket, yet has the volume of a jersey, all at a weight of 278 grams in a size Medium. The incredible wind-blocking front also stops water, while the dense but light insulating fleece delivers exceptional fit, warmth and comfort all around. Highly effective between 50 and 65°F, and manageable even a few degrees colder, the Trasparente 4 can be worn with various weight base layers for even more range, especially in dry conditions.

Blocking wind, onrushing cold air, and moisture from above and below is crucial in a full-on wind jersey. For the Trasparente 4, Castelli uses the incredible flexible, thermal Windstopper X-Lite Plus fabric as the barrier found on the front-facing chest and arm panels. This exceptional 4-layer fabric is 100% windproof, nearly waterproof, yet insulates and breathes at high levels. The level of protection is astounding given the 4-way stretch flexibility. This allows the designers to truly build a lightweight piece with protection without compromising fit, comfort, and freedom of movement.

For the back arm and rear facing panels, Castelli has chosen their Warmer fabric. The soft fleece inside traps heat and releases moisture at a high level without being bulky or stiff. The 100% polyester material uses hollow core spun yarns in a proprietary weave to achieve incredible performance. Normally fabrics that wick so well are challenged to retain warmth, especially with some air exposure, but Warmer strikes a perfect balance while still being compressive, with just the right stretch for ideal race-cut fit. All stitching is all flat lock while the seaming is kept off normal areas prone to chafing. The YKK Camlock zipper locks in place perfectly, and the pull is easy to grasp and use with gloves on. A left chest pocket with vertical zip is deal for electronics or compact food items, and the three-pocket pro-preferred rear pocket structure reassures that this really is a jersey, regardless of the level of protection. Even the soft, wide Jacquard internal waist band is perfect. It holds the piece in place, yet never feels bulky or annoying. Reflective detailing adds an element of safety and rounds out the design.