The Stebcentre is a live or dead center design bit with a circle of milled sharp teeth that bite into the workpiece securely. Highland Woodworking has a deal on the Sorby 1-1/4″ MT1 Stebcentre for $59.99.
In the case of this tool it is a live center held in the tailstock. Sorby claims it works well for eccentric turning between centers and any job where you want more positive bite than a standard center provides. Watch the videos for more detail of their use. Also, it looks really mean.
Sorby Stebcentre, 1-1/4″ 1MT [highlandwoodworking.com]