This is the Great Planes ElectriFly Power System Brushless Motor Mount. This attaches to the firewall and the electric motor attaches to this mount.
Direct replacement for the Great Planes GPMG1041 .20-.48 (3.3-7.9cc) and GPMG1061 .40-.70 (6-11cc) glow mounts. Perfect fit for both 35mm Rimfire Out-runner 28mm Ammo In-runner motors
Universal motor mounting bolt pattern insures an easy fit with any brand of motor. Lightweight aluminum construction for added durability. Unlimited adjustability from 2.1 - 3.1 in. (56 - 78mm) For medium motors
Length : 2.53 in. (64mm)
Width : 2.18 in. (55mm)
Height : 2.18 in. (55mm)
Weight : 2.3 oz (81g)
Mounting hole dimensions : 1.325 in. x 1.325 in. (33.65 x 33.65mm)