Hyperion Z-Series
DataSheet

The magnets are especially made for the Z Series motors, and are rounded

on both bell and stator sides. The result it that contact area with the bell is complete, and this has two benefits:  First, heat transfer is maximized, so the magnets are much less subject to damage from overheating.  Second, the full contact with the bell on one side, and matching curvature to the stator on the other, means that the magnetic flux lines are complete and optimally shaped;  this means higher efficiency, lower incidence of motor stalling, and smoother starts.  The magnets themselves are produced in one of the foremost factories in the world, and are the latest type, featuring both an extremely high temperature rating and high magnetic strength.  They are retained by fingers in the bell-end, and attached with a special high-temp glue made for the Japanese space program.  We think it's just about impossible to throw a magnet, or termperature de-mag these motors, and we've tried very hard...  Finally, the high-speed, shielded stainless bearings in the Z Series are made by NMB Japan;  expensive for Hyperion to install, but well worth it for smoothness and longevity. As you'll see in the specifications and prop data, the Z-Series have very high power-to-weight ratios.  The Z2209-32 at only 41.7g, for instance, is a tremendous performer on 3S li-po and 10x3.8 APC SF prop in E3D models weighing up to 350 grams.

          Z-2205 Series Data              Z-2209 Series Data               Z-2213 Series Data
 

As you can see, the shaft arrangement makes it easy to front or backmount the motors, and use either a M5 x 3mm collet adapter or a prop-saver adapter.  The shafts, retained by setscrew, are easily replaceable in the event of a crash, and are available for order.