The Marsblade High Performance Sonic 608 ABEC7 Bearings are elite level bearings for your Marsblades or your other standard roller blades. Sonic ABEC7 Bearings are made with precision-honed chrome alloy steel races and balls for incredible speed, rubber seals, and stepped inner races to defend against dirt and debris and synthetic gel and polymer cage to dampen noise and vibration. These bearings are sold in a pack of 16 and fits Marsblade Labeda wheel sizes 64mm, 68mm, 72mm, and 76mm (one size fits all), and will fit many other brand of wheels.