One tube to rule them all! Are you riding a mixed wheel size mullet bike? Can't decide to bring a 27.5 or 29 spare? Or do you just want to be a trail hero saving others with your versatile tube that fits both 27.5 and 29 ? The new MTN MULLET tube takes the guess work out of which size tube you should pack. At the drop of a hat this tube is ready to take care of business up front or ride the party in the back. Specialized Mountain Mullet Tube Bicycle Tire in Black