This has been a really great addition for me. I bought a Bosch impact drill to punch holes in concrete. (Which it does very well) But sometimes I need to drill big deep holes in hardwood and larger pieces where my drill press just can't do the job. You need plenty of torque and a way to hold the drill tight like a bulldog in spades provides. But the Bosch hammer drill in its native form lacks the ability to grip conventional bits. Here this cartridge is an important addition. It fits easily into the cam of an SDS-Plus style impact drill, and with the traditional chuck, conventional drills can now be used. You'll have to remove the protective rubber sleeve that surrounds the chuck to use larger bits, but it's not that difficult and it's fairly easy to replace. I assume the guard is for a mechanical chuck when drilling into metal or other material that could damage the chuck's gear?) I should also give a plus to the quick-adjust mechanism, which allows you to quickly change the jaw opening and then switch can use the wrench for a firm grip. Oh, and don't expect to use it with the percussion aspect of the drill. It's not designed for that. The oscillating motion loosens the jaws even with the hardest turn of the wrench. It is designed for basic twist drill work and works very well for that.