If you want a 12mm reamer, Fox makes one
http://www3.towerhobbies.com/cgi-bin...&I=LXNL18&P=ML
It features a 1/4" pilot reamer to help start an accurate ream. It is then stepped to 10mm and 12mm. It also features steel construction and has four reaming cutters. Includes a slide-on handle.