Additional Product Image Thumbnail Size

Hi All,

Anyone can help me with this? My Opencart is 1.5.2.1.

I will like to change the Additional Product Image Preview Thumbnail Size below the Product image.

As my image is vertical, it seems to be squashed in the thumbnail. Appreciate anyone can help me with this.

And changing the size in System-> Settings->Image does not help.

I assume need to change in stylesheet.css but i not sure where is the code to change this.

Oh. And i have cloudzoom vmod installed.. Please advice!!