This is a spilt nacelle unit for 25mm EDF with 1/16" (1.6mm) slotted side mount. This allows you to mount the unit on a 1/16" ply piece and run your wiring internally. The side mount has a symmetrical airfoil shape, tapering at the rear.
This unit has been designed with speed in mind. The intake flange is symmetrical and sharp. The hub (if 13mm long) will protrude ~2mm from the face of the Nacelle. It has 4 motor screw mounts for extra stability and a longer motor housing to give greater support. The rear section of the Nacelle will align your exit tube to the required size of 85% FSA.