Atlas Black Out Built-in Bearings
“When axle nuts are tightened down on bearings the result is often compression of the interior bearing spacer. This introduces slop into your setup (especially over time) and detracts from the precision that a bearing spacer is intended to provide.
The flared spacer built into the Atlas Blackout Bearing increases the surface area contact between the two bearings, providing additional support and alleviating the negative compression effect. This makes for less slop, a more precise ride and an increase in the life of your bearings.”