During the life of the Persian Empire the status of the cavalry had grown enormously, and by the time of Darius III it was both a noble and a royal pastime to ride. With much rugged countryside in the Empire the Persians could call upon many excellent riders, and though these would have come from many different peoples, it seems their appearance would usually have closely matched that of the Persians themselves. There was no rigid definition of medium cavalry of course - those that could charge formed infantry were termed heavy, and those that could not were light, although even these terms are not necessarily something an ancient Persian would have used.
The four poses are all appropriate for this type of cavalry. One man is using a javelin as a thrusting weapon while another has drawn his sword for close-quarter combat. A third is carrying a javelin ready for either thrusting or throwing, and a fourth is waving an axe. All these poses are very straight-backed and so do not suggest much movement, so unlikely to be immediately in front of the enemy, but everything here is reasonable.
Two of the men have linen or leather armour in the style of the Greeks, which was quite common, and the other two have no apparent armour, though contemporary sources say armour was often worn hidden under the tunic in this manner. Their costume is typically Median, with all wearing the cap as seen on the Alexander mosaic and elsewhere. Two have a sword as a sidearm while the other two have long knives, so everything about the costume and weaponry looks right. There is evidence that some cavalry was rearmed with much longer spears around the time of the Persian confrontation with Alexander, but this seems unlikely to have progressed far before the death of Darius, so the javelins shown here are of the correct length.
Between these four figures all the principle features of normal Persian cavalry are displayed, so the result is some very nice and very accurate models. Detail is very good and the poses are all useful. We felt that the axeman had his weapon perilously close to his own head, which looks a little odd, but our only significant criticism is that only the swordsman sits on his horse correctly. Due to excessive plastic on the inside of the legs on the other three, all become perched some way above the saddle. A little carving away of the inside legs solves the problem, but it is very unusual for HaT cavalry to not fit their mounts properly.
The first of the horse poses above was not to our taste, but the second looks natural, and the saddlecloths and bridle are all correctly done, as are the closely cropped mane and tail tied towards the end with a ribbon. Although only four poses is never going to cover a subject in much depth, all these poses are reasonable and include all the most common weapons. No one here has a bow, which is perhaps not surprising as the bow was less common by the time of the Alexandrian invasion, but essentially, with no rules about definitions, these 'medium' cavalry could augment units of either light or heavy cavalry, producing some pleasing variety for your Persian cavalry.