Thanks Mark, The mounting holes measure 3 mm across the top. I will check out both sets of screws (3mm and 4mm). The link has the same fan unit as I have the only differance is the color of the fins on the motor. I will have many questions as I have no experance with electric flying. I have a programable speed control andf i will need to know what settings to use. Ramp up hard accel. or soft? Break or no break? Soft or hard cut off. Thanks again