Tera F450 HJ450 Quadcopter Kit Frame Multi-Copter for KK MK MWC we adopted M2.5 arm fixing screws (shoulder screw) with same spec to the DJI F450. with built-in circuit board for ESC power distribution, less parts but strong structure to let user for maintenance more easy . The mounting holes design can fit for different controller board e.g. KK, FF, MK, MWC in the RC market, it can fulfill different kind of user need e.g. FPV. Recommend combination with: Motor: A2212 800KV-1400KV. ESC: 20A. Recommend combination with: Battery: 3s 1800mah-3600mah. Propeller Size: 10x4.5 in or 10x4.7 in.