This is the Xnova XTS 4525-530KV YY Brushless Motor, with a 6mm “Type A” 36mm shaft. The Xnova XTS series motors are developed and optimized for pure performance. The Xnova XTS series 4525 models are specially designed for 630-700mm helicopters to deliver an insane power to weight ratio. The 530kV model is recommended for extreme 3D flying and is optimized for 12S applications. All XTS motors are 100% hand-wound and each motor runs through a complete quality control test before shipping.