David Weaver
10 seconds of turning those holdfasts around and making spirals of 80 grit spirals on the surfaces will make them hold in a 4 1/8 hole with no counterbore.

They don't hold well without being scuffed. They probably don't hold well if someone babies scuffing them - they're bent pieces of spring steel, no reason to baby them.

For the money, they're fantastic. Even without regard to the money, they're fantastic. It's up to the person who buys them to decide what finish they need. Nothing special, just hold coarse paper in hand on the shaft of the holdfast, squeeze and turn.