Specs:Rpm/V: 1000kvShaft: 3.17mmVoltage: 2S~4S (7.4v to 14.8v)Weight: 52gWatts: 210wMax Current: 21AESC: 30ASuggested Prop: 8x4 (4S) ~ 10x7 (2S) Mounting Hole Bolt Circle: 16mm or 19mm