Standard refacing includes leveling the table, applying a parallel facing curve to both side rails, and ensuring the tip and side rails are even and match the shape of a standard reed.  The length and type of facing curve can be altered to affect the response of the mouthpiece, and the baffle can be shaped to affect how bright or dark the mouthpiece sounds.  While a mouthpiece can be altered to match the specifications of another piece, there is no guarantee that both pieces will play exactly the same once the work is completed.