Castelli's line of packs and bags has proven popular for their style, features, and pure performance. it was only common sense that under saddle bags would be part of the equation. The Undersaddle XLPack is rectangular, with a sleek design that disappears under most saddles yet carries plenty of gear and has an external bottom mini-pump sleeve. The XL pack is affixed by two simple hook and loop closures, one that wraps around the saddle rails, and a second secures around the seatpost. Highly water resistant material also fights oil and grease, as well as other road spray delights from staining the pack. The main opening zipper is a sealed affair, and blocks nearly all potential moisture when closed properly. An extended pull hangs from the zip itself, which has little garage when fully closed.

Castelli lines the interior bottom of the pack with red nylon, which stands out against the black exterior fabric, which makes it much easier to distinguish stored gear. A small internal mesh sleeve pocket is great for small items that you don't want to interfere with your tube, or get lost in the mix. The XL holds the essentials, and has room for extra CO2 or tube, perfect for most road riders going out alone. Add in the mini-pump sleeve and you can be quite self sufficient. A simple Scorpion logo and reflective print accents add some flash, flair and safety. This clean-looking under saddle pack fits right in with the Castelli aesthetic and practical functionality found in their bag line. Though not waterproof, it blocks most water and is competitively priced, at a high level of overall quality in materials and construction.