This is the Xnova XTS 4530-525KV 4+5YY Brushless Motor, with a 6mm “Type A” 38mm shaft. The Xnova XTS series motors are developed and optimized for pure performance. The Xnova XTS series 4530 models are specially designed for 700-800mm helicopters to deliver the highest power to weight ratio. The 525kV 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.