Image width of 50% on product page like in demo

Hi, how are your settings for the image width of 50% like in the demo of Symbiostock Express. I can’t reproduce them. Here is my site: http://www.bildtankstelle.de/bild/wooden-cloud-die-architektur-der-wuensche-von-martin-steinert/

The width I can see is only

.col-md-5, .span5 {

width: 41.66666667%;

}