This steel and aluminum jig is used for drilling stocks to accept sling swivels, and is capable of handling material from 1" to 5-1/2" in diameter. The stepped drill bit includes a stop collar so that needless drilling is avoided. Drill bit includes stop collar and instructions are included. Notes:Jig will hold material from 1" to 5 1/2"Step drill bit is 0.15" in first section and 0.25" in second section (and shaft)