This is the .50 Brushless Electric Motor from O.S. Motors. FEATURES: For airplanes using a .50 size 2-stroke engine or 4-stroke .91 size engine Centrifugal fan design with angled ventilation holes draws air through the motor and across the windings and magnets for improved cooling INCLUDES: .50 Brushless Electric Motor with Backplate, four Phillips Head Mounting Screws, 4mm Gold Plated Male Plugs attached to leads, three 4mm Female Plugs with Shrink Wrap, Prop Adapter and Instruction Sheet REQUIRES: 90A brushless ESC SPECS: Rated Power: 1550W Rated Voltage: 25.9 - 29.6V Rated Current: 50 - 60A Maximum Current (10 sec): 90A No Load Current: 2.0A Phase Resistance: 27.5 miliohms Maximum Efficiency: 85% kV: 375 Poles: 14 Shaft Diameter: 0.23" (6mm) Shaft Length: 0.45" (11.5mm) Weight: 14.3oz (405g) Lead Wire Length: 4.3" (110mm) Length of Motor Can to Backplate: 2.3" (57.5mm) Diameter of Motor Can: 1.98" (50mm) Length/rear of Motor Can to Prop Washer: 2.9" (74mm) Prop Washer Diameter: 1.06" (27mm) Thickness of Motor Mount: 0.16" (4mm) Width of Motor Mount: 2.67" (68mm) Height of Motor Mount: 2.67" (68mm) Performance for this motor with different props and LiPo cells is as follows (all data with 100A ESC): Prop Size Max Electric Current LiPo Cells 14 x 8 45A 8S 14 x 10 56A 8S 15 x 8E 50A 8S 15 x 8E 38A 7S 16 x 8E 62A 8S 16 x 8E 47A 7S 15 x 10E 60A 8S 15 x 10E 47A 7S 16 x 10E 57A 7S 16 x 10E 43A 6S COMMENTS: Nomenclature is defined as follows: 0MA means 0.S. airplane motor First two digits are the rotor diameter Second two digits are the length of the magnets Last digits indicate the kV of the motor jxs 05/11/11 ir/jxs