We have two of these at Gulfstream & I have seen it work, saved a couple guys fingers. The one I saw get his finger into it didn't even draw blood. There is a cartridge to replace after the saw stops & goes for around $300.00, but well worth it to save an injury. If you dont remember to turn this feature off when cutting any conductive material such as metal, you'll blow the cartridge & piss off the boss.