Haven't taken it off in 17 years.

It really works and is by far the most valuable accessory for the Dremel. It closes down to near 0 for the smallest of drill bits (much smaller than a sewing needle) yet still holds larger bits than the "large" hex collet. It is well made and durable, withstanding everything from concrete and tile dust to oily metal shavings. It must be tightened with considerable force to resist slipping under heavy use but that's to be expected.