The Betta RoS Jacket from Castelli is an ideal shoulder season jacket with a thin but effective build, great stretch and protection. This lightweight wind and splash barrier provides a surprising amount of warmth for it's weight, taking advantage of Polartec NeoShell's windblocking capabilities. The cut is race fit for performance on fast autumn and spring rides on any terrain but has plenty of stretch for comfort and doesn't feel restrictive. Given it's purpose as a high performance piece, you want a conforming fit to save watts and prevent billowing.
In the Spring or Fall you don't want to sacrifice the nicer days of amazing riding, but when it can hard to gear up when all you are used to wearing is jersey. That's why Castelli made the Betta RoS Jacket. It is more like a long sleeve jersey with rain and wind protection and more jacket-like features. The designers used the lightest, stretchiest fabrics, in this case Polar NeoShell on most forward facing zones, and Castelli's own Nano Flex Light woven, water repelling fabric on the rear and in areas where softer stretch is optimal to make a jacket that cuts out most of the wind, remains highly breathable, provides remarkably high levels of water protection, and just basically disappears so you don't really notice it. You know, like a jersey.
This is a performance piece, so the overall concept is clean and focused on the task at hand. There's nothing superfluous on it, unless you consider the big reflective panel on the back to be unnecessary. The collar is tall, soft, and has a internal flap to protect you from the YKK Vislon zipper. The zipper is covered by an external draft flap almost all the way to the bottom. It stops several centimeters above the hem to avoid excess material overlap when you ride in an aggressive position. Of course the cycling specific cut features a short front, long rear, and extended sleeves as well. The 3-section rear pocket structure offer generous storage and easily reachable access. Castelli has adorned the Betta RoS with a clean, sharp look, with dominant colors, an accent swath, and minimal logos.