beware of those cheap replica...
actually there are many parts inside the iphone which sticks to the back housing...
so if you buy those cheapo, it's just a piece of back housing minus all the small parts stick to it...so you have to take it out and install the parts urself on the new back housing...
i lost the link for this but i can remember...that's why if you buy original iphone back housing replacement, it will come preinstalled with all those black tiny parts sticking at it...but it cost a bomb!