Well this was an interesting find. An integrated nut and dust-collecting updraft impeller on an ER20 collet.
I’ve seen evidence suggesting they help a lot on larger systems. The ER20 is smaller though and that reduces the tangent air velocity at the slots, reducing its suction potential for the same RPM.
It’s only going to work with LONG bits, because the impeller extends about 1" below the collet face. So a bit needs to longer to come up with another 1" clearance, which seems like it would make it much easier to break bits below 1/4".
It’s also aluminum down to the threads, not steel like the normal nut.
I didn’t have any bits with me at the time (NEVER run the spindle with a nut (or nut and collet alone) without something shanked in a collet. The nut can unscrew itself and go flying. Having not experimented yet, I’m not sure it’s even safe to use as intended. The red thing is a spanner wrench required for this type of nut.
I left it in the kiosk to experiment with.