Why this ? image height

Image height is not limited, all depends on image aspect ratio.

Image height is not limited, all depends on image aspect ratio.

How to add  max height

@johi
I would not change height of image, but parent box.
Try this:
.products.grid .simple-prod .img-wrap, .white .simple-prod .img-wrap {max-height:500px;}
Or do not use force image aspect in media settings, you might use "best crop" instead