One piece covers will bubble up over the edges, between the glass and the aluminium, over the Apple logo, and the "Apple" word. You can get three piece back covers on ebay for very cheap, they arent that bad quality, and they wont bubble up on the edges, but you'll still have bubbles over the logos. If you dont want bubbles you have to get covers that requires wet installation, like Phantomskinz. There's a thread about it, with pictures, looks really great, and no bubbles, as far as i can tell from the pictures.