It happens to us occasionally; Bluebird skies, mid-70s temperature, no one is on the trail, and 10 miles into our singletrack fantasy, we get a flat. With two Cutter Premium 29in Mountain Bike Tubes in our repair kit, the crisis is averted and we are back on the trail in a few minutes time. Keep Cutter Premium 29er MTB Tubes as a backup in case of a downer premature air release. The last thing you want is to be bummin' from the side of trail. Cutter Premium 29in Mountain Bike Tubes come with a presta valve and removable core. The 29 x 2.3in tube comes in a 4-pack so you can keep to in your repair kit and two in the car.