This is the 2815-5400 Slotless design high efficiency, High performance motor for replacement of 500/550 type can motor, Direct replacement for B40S, Aveox27/26, and Astro05, Gear motors are suitable for small electric trainers, sport fun flyers, Direct drive motors are best for ducted fans & pylon racers where high rpm is a must, Use HA2815-5400 with a gear drive. For light electric planes under 70oz(1960gr) Motor specs: Diameter:27mm, length: 38mm, Weight: 86gr Shaft:4mm, MaxCurent 25A KV:5400 Power: 250W