Setting Mini-Thumbnail Size

The mini-thumbnails that sit below the thumbnail on the 'Product Detail' page are clicked on to change which thumbnail is viewed (see smaller red & black backpack images under larger version on attached image) .

I'd like to be able to change its size. Where is its size determined? Can it be changed?

Mini-thumbnail.jpg

design/themes/THEME/templates/views/products/components/product_images.tpl

{assign var="th_size" value=$thumbnails_size|default:35}

Change this value and clear cache