One of the benefits of using a Prologo saddle is the Italian maker's systems approach to accessories. Get the optional U-Clip, which plugs right into the rear of any current Prologo saddle and you can quickly snap on a U-Bag Saddlebag in one of two sizes. This provides several advantages. First, the clip function allows you to remove the bag from beneath your saddle, dig through its contents and replace it all without ever fiddling with attachment points at the seat rails. Second, because there are no seat rail straps, the bags never waddle or sway while riding, or catch you on your inner thigh the way bags that strap to a seatpost can. And for that same reason, if you need to throw your bike up on a stand the bag can be removed in a nanosecond.The larger Prologo U-Bag has about a half-liter capacity, and is large enough for stowing a spare gel or two, multi-tool, levers, and a tube. The smaller model is only for the bare essentials like a tube, levers, and some cash.The Prologo U-Bag is available in two sizes. Both feature rear reflective tape, for great visibility and attach to the tailpiece of any Prologo-branded saddle via a (required) U-Clip accessory mount. The U-Bag is also compatible with Topeak's QuickClick connection system.