Size: 4, 5, 6 and 8 inches Double 6202 bearings and locating tube design, special plastic (PP) core and surface uses 92° TPU, T-shaped hook core ensures the TPU not easy to fall off The arch-shaped of the core can enlarge the loading capacity and have buffering power to shock, more flexible running Deepened the position of bearing and flat face design can enlarge the contact with the ground to make larger and more stable loading capacity Main rig: medium-heavy duty rig Other rig: heavy duty mini rig/medium-heavy duty shock resisting twin caster rig Loading capacity is 180 to 360kg abcd