[Dr_Jengo]

Usually with the Regular, they are available from and sold by other retailers like BigBadToyStore and others that I can't remember right now..

Exclusive will only be available on SideShow's website. Their way of making sure they give collectors reason to purchase directly from them. Like mosavon mentioned, they are also more limited. These Exclusives can range from an entirely different costume to an extra gun, like in this case.