Their small dolls, with a centaur lower body that has four movable legs. Each having different traits that match the monster their crossed with, some having horse like tails some not, and some have wing. Their clothing is also mostly made out of plastic rather then fabric.
The first four Fright-Mares' packaging that are released did not have a pop-out artwork similar to the regular Monster High dolls. The next six releases' packaging was modified to be similar to all the regular Monster High doll packaging.
As a consequence of the 2016 reboot, two Fright-Mares have gone unproduced: a griffin-based one and a dragon-based one. This information was temporarily available on Walmart's website.