Fixed size of Flexslider

Let's say you wanted a fixed size of 200px by 200px. Add these properties to the following selectors in the flexslider.css file and you should be good to go:

.flexslider {
    width: 200px;
    height: 200px;
}

.flexslider .slides img {
    width: 200px;
    height: 200px;
}

Hope this helps!

The element with the class ".flex-viewport" is the container of the slides, that element adapt his height to the taller image in the set, the trick is set all images height's to 0 except the one that is in the current slide which is inside the li element with the class ".flex-active-slide" that flexslider script toggle when slides exchange positions, the only bad thing about this trick is that the toggle of the class occurs after the new slide is put in the new position then a stutter occurs, but you can deal with that by using some javascript binding some toggleClass to the same event that trigger the slide change, help to be helpful.

.flex-viewport  li:not(.flex-active-slide) img{ 

height: 0 !important;
}