This is actually an interesting question I already answered partially HERE
www.pornbox.com is like shopping mall, it is the website where users actually purchase the content.
Other websites, where you can watch the trailers but you do not actually purchase the content, are just promotional tours, meant to "catch" new users to bring on to pornbox.com.
this is the list of some promotional tours
www.analvids.com
www.giorgiograndi.com
www.bustedt-girls.com
www.giorgioslabs.com
www.xfreaxx.com
www.thewondertoysanaltraining.com