The Quartz QZ204 is a similar size and specification as the Hitec HS82MG and a very worthy substitute in that it has brass gears and a single ball race bearing. The HS82MG is plain bearing with aluminion alloy gears Wing Servo Mount SM020.
Specification:
Voltage: 4.8 - 6 volts
Dimensions (mm): 12.0 x 29.6 x 29.8
Weight (grams): 17.5
Speed (sec): 0.13 (4.8v) 0.11 (6v) /60 deg.
Torque (Kg.cm): 3.0 (4.8V) 3.5 (6v)
Gears: All Brass
Ball Raced: Single