Marathon Plus Evolution Wheelchair Tires operate between 85-145psi and employ SmartGuard. SmartGuard is a Flat-less tire technology that protects Schwalbe Marathon Plus Evolution Wheelchair Tire liners from punctures while offering new levels of comfort and superior rollability among pneumatic tires. Now, you can safely navigate through dangerous obstacles like broken glass and count on Schwalbe Marathon Plus Evolution Wheelchair Tires to stay strong. Schwalbe Marathon Plus Evolution Wheelchair Tires are user friendly with 2 grip smooth sidewalls and compatibility with standard tubes. We would also like to introduce BlacknRoll - SCHWALBE's own revolutionary compound that lets you to wheel these black tires across indoor floor without leaving skid-marks. Available in 24", 25" and 26" size. Price is for a set of 2 tires