Bags

The Medio is water-resistant and made of an extra durable nylon fabric that's impregnated with thermoplastic polyurethane (think frogman raft). It's secured under the saddle with a wide nylon strap (like seat belts in cars).

The Dual is small enough to nestle under a seat without scraping against your thigh, yet it’s big enough to hold two 700C tubes and two CO2 cartridges, plus an inflator.
•0.44L Capacity
•Leather wear patch to protect from seat post abrasion

The Uno is small, with only enough space for a road inner tube and CO2, and maybe a couple of Allen wrenches. It also fits under the saddle nicely when cinched tight.
•0.26L Capacity
•Leather wear patch to protect from seat post abrasion