"The Evoc Tour Seat Bag is built from a water-repellent polyester and nylon shell that keeps a multitool and spare tube dry through wet weather and road spray. A Hypalon-reinforced front panel takes the wear where the bag rubs against the seatpost, so the shell itself stays intact ride after ride. What Our Gearhead® Experts Are Saying:""I load a multitool and spare tube in the main compartment and forget the bag is even there through a full gravel day. It doesn't sway or knock against my leg on climbs the way an overstuffed jersey pocket does. Cinching the compression strap down on lighter loads keeps it snug against the seatpost instead of swinging loose."""