This is the E-Flite Power 25 Brushless Outrunner Motor 870Kv.

Features:

Equivalent to a 25-size glow engine for sport and scale airplanes weighing 3–5.5 lb (1.4–2.5 kg)
Ideal for 15-size 3D airplanes up to 3.5 pounds (1.6 kilograms)
Ideal for models requiring up to 600 watts of power
High-torque, direct-drive alternative to inrunner brushless motors
Includes mount, prop adapter and mounting hardware
External radial rotor design—6mm shaft can easily be reversed for alternative motor installations
Slotted 14-pole outrunner design
High-quality construction with ball bearings and hardened steel shaft
Quite, lightweight operation
You Will Need:

40–45A brushless ESC
3S–4S Li-Po or 10- to 14-cell Ni-MH/Ni-Cd
11x8 to 14x7 prop
Specs:

Type: Brushless outrunner
Size: Replacement for 25-size glow engine
Bearings or Bushings: One 5 x 14 x 5mm Bearing, and Two 5 x 11 x 4mm Bearings
Wire Gauge: 14
Recommended Prop Range: 11x8 to 14x7
Voltage: 12—16.8
RPM/Volt (Kv): 870
Resistance (Ri): .03 ohms
Idle Current (Io): 2.40A @ 10V
Continuous Current: 32A
Maximum Burst Current: 44A (15 sec)
Cells: 3S-4S Li-Po or 10—14 Ni-MH/Ni-Cd
Speed Control: 40—45A brushless
Weight: 6.7 OZ. (190 g)
Overall Diameter: 1.40 in. (35mm)
Shaft Diameter: .20 in. (5mm)
Overall Length: 2.10 in. (54mm)