The latest entry in the Montana Colors and Upper Playground series of artist cans is in, and the collaborators this time are El Mac and Retna. The two street artists have teamed up before, and have actually just released a book, ‘Alianza’, dedicated to their collaborative work. There’s got to be some kind of internal conflict in everybody who picks one of these cans up, do you keep it as a collector’s item, or do you use it? Whatever you decide to do, the can and ‘Alianza’ are both available from Upper Playground retail locations and the online store.