It is a 1.25-inch vacuum nozzle. It is toothed to allow for sucking even when it is used on flat surfaces. A normal “non-toothed” nozzle will lose suction if flat against a surface. But this nozzle will still have strong sucking forces to suck up whatever mess you're cleaning up.

For me, it works great. I've used it on my fabric couch, my title floor… and my dog loves getting vacuumed too.