These Cloud Wheel Rovers are special designed for Backfire Hammer and Sledge.
The rims on the wheels are special designed, which are different from other brands' 165R cloud wheels sold by the wheel manufactures. In other words, if you bought a set of 165R cloud wheels using 608 bearings from other sources, they do not fit with the hammer or hammer sledge directly.
The bearings to fir these wheels are size 6000 bearings to fit the 10mm truck axles, not traditional 608 skateboard bearings.