3 Planetary Gears. Steel:38 11mm,Hole Dia. 8mm,Bearing 608. Steel+Plastic:38.5 11mm,Hole Dia. Copper +Plastic:38.5 11mm,Hole Dia. Material:Nylon,Steel,Steel+Plastic,Copper+Plastic. Types:Nylon,Steel,Steel+Plastic,Copper+Plastic.
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