If you look over in the "Lenco" thread you will find some info on this.A Rega arm has an effective mass of 11gms and this is considered medium mass.A MM cartridge really works best on a light arm and an MC is more suited to medium mass arms like the Rega(generally speaking).The Sumiko is a great choice for the Rega and is also around 10Hz cartridge resonance which is near perfect.
