My mortise gauge attachment easily fits into the body of my Rob Cosman Marking Gauge and you instantly have a mortising gauge. The attachment also fits my "Cosmanized" Woodriver Marking Gauge and  any other marking gauge with a 5/16" inch hole .  The attachment comes with:

• 1/8" hex wrench to remove the cutter head for sharpening.

• A brass knurled locking handle

• An O-1 hardened cutter.

Why not save yourself set-up time and purchase one of my Rob Cosman Marking Gauges so you have a dedicated mortising gauge?