The Castelli Fly Long-Sleeve Jersey is a lightweight thermal that we like for rides in the 50s and 60s. The Fly T-SL fabric is super-light and stretchy and brushed to add a little warmth for chilly mornings and spring and fall rides when we're riding fast and it's a little bit chilly. The three back pockets provide a good place for us to stash our essentials while the collar-less cut and full-length zipper help us regulate our temperature.