This is the Great Planes ElectriFly Power System Brushless Motor Mount. This attaches to the firewall and the electric motor attaches to this mount.

Features:

• Perfect fit for both 28mm RimFire, Outrunner and 24mm Ammo In-runner motors
• Universal motor mounting bolt pattern insures an easy fit with many brands of motors
• Lightweight aluminum construction for added durability
• Unlimited adjustability from 1.6-2" (40-51mm) 
• For small motors

Includes:

• One motor support for small motors
• All assembly hardware

Requirements:

• Mounting to the firewall and attaching the motor

Specifications:

• Length: 1.65" (42mm)
• Width: 1.97" (50mm)
• Height: 1.44" (36.7mm)
• Weight: 1.2oz (35g)
• Mounting hole dimensions: 1.19"x1.19" (30.2x30.2mm)