扣環，滾子軸承，9x20主軸軸承，外側

That shield ring fits so snug against the roller bearing that I stopped worrying about grit getting in there. Metal feels solid and the machining is clean, no burrs to catch on.

Slid onto the shaft with zero play and it sits flush against the bearing just like it should. The steel feels solid enough to keep out sawdust and grit for a long time, which is exactly what I needed for my spindle.

The machining on this ring is precise—it seats flush against the roller bearing without any wobble, which keeps the spindle snug. I appreciate that it doubles as a shield against grit, so the bearing stays clean during heavier cuts.