The Adapter Hole of the DJI Style Propeller is different to normal style (Circle). So you must make sure you have the DJI Style Motor Propeller Mount before purchase.
** above information was approximately measured as on 2014/06/06, it may vary from time to time.
Propellers (especially Plastic & Nylon) are not yet balanced by factory (you think about the labor cost then you will understand why). Carbon Fiber Propellers however have usually been paired but "Paired" does not mean balanced (pair the CW and CCW props *close* to the same weight). So you need this Propeller Balancer to balance the prop by yourself, and it is really a must tool if you fly multirotor copters. Please watch the video below for usage.