In case you were wondering how Sandbar's body dimensions compare to a typical adult mare.

These were cropped from a screencap toward the end of School Daze part 2, where they are both standing in line with each other in profile.

Main differences are his facial structure, more boxy body (slightly longer than AJ's), limbs narrower and slightly longer, and neck slightly longer.

AJ's head is rotated downward/forward a little bit, giving her the illusion of being the same overall height. If her head was tilted back like Sandbar's so that her ear was vertical like his, she'd be noticeably shorter.