(updated 11/08/05)Since ElectriCalc was first introduced, the number of motor constants has more than quadrupled. It is difficult to keep up. Sometimes *you* need to do a little detective work. Search the web. Ask on forums. Measure them if you have the means, then *share* the information.
The entry under the heading of M indicates the magnet material and brushed or brushless. M
F = Ferrite magnets. This is a cheap material and associated with lower efficiency motors. They don't hold up to heat well. C = Cobalt magnets. These are expensive, stronger magnets. Motors with these magnets are generally powerful with high efficiency. Best resistance to high temperatures. N = Neodymium magnets. Expensive, somewhat stronger than Cobalt, but with lower temperature tolerance. Most high-quality motors are being manufactured with these magnets. + = Brushless.