Set of two counterweights, metal endstub, and precise 0.1g Vertical Tracking Force adjuster for Rega RB-250 and RB-300 tonearms and their derivatives. One counterweight matches cartridges of 3 to 6g mass, the other is for cartridges of 7 to 13g. The center of mass is at the stylus level, thereby increasing tracking and reducing record wear.