The Marsblade O2s - the next chapter in world leading off-ice training. Same ice feel. Same results. Built on our proven formula, now with new and improved design and next level features such as: Optimized Rocker Setting Customize your skating feel with interchangeable inserts (sold separately) for a truly personalized training experience. Hi-Lo Wheel Setup Engineered for maximum speed and maneuverability, all without increasing height. Enhanced Torsional Stiffness Improved energy transfer for a more powerful stride. Top-End Revision Clinger Wheels Powered by the patented Flow Motion Technology, which creates a unique rocker that replicates the radius shaped ice blade to simulate skating on-ice. The O2s will challenge your balance, simulate ice skating and activate the right muscles to improve your on-ice performance. Box Content - Marsblade O2 Chassis x 2- Revision Clinger Outdoor Wheels (82A hardness) x 8- Swiss Bearings x 16- Rocker Inserts x 1 pair- Wheel Axles x 8- Bearing Spacers x 8- Multitool x 1- Tech Manual/User Guide x 1 Wheel Configuration (mm) 80/80/76/76 (size L) 76/76/72/72 (size M) 72/72/68/68 (size S)