Neu Rotor Hard to Turn

[Shark413]

Quick question for the brushless motor wizards. I have a Tekno Neu motor and the rotor turns over very easily. I have an older Neu and the rotor is much harder to turn by hand. I heard that the Tekno Neu's had been designed like that to lessen clogging or something like that. My question is what makes the Original Neu so hard to turn over? I mean sure it has a strong neodymium magnet but the motor can is made out of alluminum and I believe the coils are made out of copper which are both non-Ferrous Metal (non-magnetic). So what is the magnet acting on to cause the rotor to be so stiff? Is there a steel sleeve holding the coils or what? Just curious, both motors work great.