Electronic speed controller (ESC) is a electronic circuit to vary the speed, direction and possible to act as a dynamic brake, of a brushless motor. This particular ESC is recommended with A2212 brushless motor (1000kv, 1400kv,2200kv). Specifications - Weight : 23g, dimensions: 45.0*24.0*9.0mm, current(A): 30-40, BEC: 3A, PWM: N/A, Li-Po : 2-3, Ni-Mh/Ni-cd : 4-10Ni-Mh, constant current: 30A Max 40A <10s, Li-Poly 2-3 cells, Ni-MH 4-10 cells auto detect break on/off, auto low battery slow down at 3.0V/cell Lipo, cut-off at 2.9V/cell Lipo.