A UBEC is needed if your Electronic Speed Controller (ESC) does not have a built in Battery Elimination Circuit (BEC). There's also a requirement to fit a UBEC where the ESC's BEC is inadequate to power the number and / or size of servos being used. The ZTW UBEC range satisfies this requirement by supporting continuous simultaneous servo operations, thus eliminating the possibility of overloading your speed controller's BEC during periods of high peak demand (as might be experienced during extreme aerobatics).
