All metal gearbox for Feigao 13084xxx motors or other 20mm diameter motors with 2.3mm shafts (Hacker B20, etc.). Included pinion press fits on 2.3mm motor shaft. Output shaft is 4.0mm and is supported by dual ball bearings. Has built-in 10mm square stick mount with integral heat sink. Includes rubber spinner and mounting screws. Weight: 28.3 grams / 1 oz (including spinner).