The Cheezeball Swiss 7mm bearings are amazing the best bearings #1 in ratings. We tested on Silicon Nitride cereamic balls, one of the strongest cereamic compounds in the world This is the same material used in aerospace, I's capable of 35,000RPM at over 500 degrees!! We paired these having No Rust! Put it this way these are THE SMOOTHEST, LONGEST LASTING BEARING EVER!!!!!