Ritchey WCS Carbon Matrix C220 84D Stem - 120mm 31.8 Clamp -6 1 1/8" Carbon BLKRitchey WCS Carbon Matrix C220 Stem 120mm 31. 8 Clamp 6 1 1 8" Carbon Black. With the Ritchey WCS Carbon Matrix C220 Stem you really can have it all. Easy to install and remove thanks to a press fit handlebar clamp interface and forward facing hardware. The C220 handlebar clamp design creates a more secure interface by wrapping a full 220 degrees over the handlebar. Bolt forces are aligned with the clamp so that the stem body embraces the handlebar