Using the calibrated stop rings on Herdim reamers enables you to trim the pegholes to a definite diameter matching precisely the final diameter of the Herdim standardized pegs. The same applies to the conical holes of endbuttons and cello and double bass endpins. The stop rings are tapered in ultimate precision according to the matching reamer and held in position via a locking screw. The fence side is slightly rounded to avoid scratches on the pegbox. The nominal diameter is etched on each ring.