Common

Approximate size of 5/16" drilled holes. Distance apart 3/4" to 7/8" center to center.

Medium

Approximate size of 1/4"‚ drilled holes. Distance apart center to center 5/8" to 3/4"

Fine

Approximate size of 3/16" drilled holes. Distance apart center to center 1/2" to 9/16"

Super Fine

Approximate size of 3/16" drilled holes. Distance apart center to center 7/16" to 1/2"