These are the 550mm Main Rotor Blades for the Thunder Tiger Raptor 30 Helicopters. FEATURES: Wood construction Pre-drilled mounting holes INCLUDES: Two main rotor blades Two blade grips REQUIRES: Installation onto rotor assembly SPECS: Length: 550mm (21.65") Width: 50mm (1.97") Airfoil: Symmetrical Grip: 12mm (0.47") Hole Diameter: 4mm (0.16") lmm 10.26.10 ir/jxs