I'm seeing a lot of posts where people are waiting for Xur to sell a certain exotic Armour piece. I thought I'd look at the chances of getting it through an Engram each week. As we know, there are 3 exotic armour pieces (one for each class) which have not yet been sold by Xur. So let's assume we can only get these from his Engrams (and possibly also from a random legendary Engram). So expressed as a percentage, each exotic Engram has a 33.3% chance of being for your class, and therefore 66.6% chance of being for another class. Which means if you are looking for a specific item (i.e: Heart of the Praxic Fire chest piece for a Warlock) then your chance of getting that from a chest armour Engram is 16.7%. If we delve a little deeper and ask "what are the chances of Xur hooking me up that Heart of Praxic Fire next week" and we can assume he won't be outright selling it; the chances of him having an Engram for that armour type is 33.3%, there are 2 types of armour per class so the chances of that Engram (which you had a 33.3% chance of getting in the first place) decrypting into that elusive armour piece are 16.7%. So finally, the chances of you getting Heart of the Praxic Fire from Xur next week are 5.56% BUT, does he sell weapons engrams? I can't remember - but if he does I guess there's a 50% chance of it being one of those, so that'd only make it a 2.78% chance to get Praxic in any week. I got lucky in the second week, hope everyone gets theirs soon.