Renders based on leaked parts of the upcoming iPhone 5 portray the smartphone as feature a 4-inch screen, though largely remaining the same as the iPhone 4 and 4S. Apple appears to have favored elongating the screen, perhaps to preserve the slim form factor, rather than widening.

The renders are courtesy of Blackpool Creative and industrial designer Bryce Haymond, who made the renders in CAD - the same software used for rendering the actual phone.

Haymond pointed out that the mute switch and volume buttons are lower than previous versions, the speaker and microphone grills on the bottom of the device have changed to a perforated circle which is similar to the iPad, and the camera and flash appear to be higher than previous models (possibly due to the increased screen size).

The major change, though, is the back panel: the render seems to have removed the glass back in favor of metal. Some users complained the iPhone 4 and 4S suffered from breakage when dropped, while the back side of the panel looked flush with the aluminum bezel. The iPhone 4 and 4S back panel extrude from the bezel, while Haymond said the iPhone 5 could be thinner with the front panel also appearing to be slightly less extruded than previous models.

The render also shows the plastic rings around the headphone jack and dock port, and a smaller SIM slot. There's no news on whether Apple will keep the volume and mute switch buttons silver, or black or white depending on the phone's color.

Of course, the leaked parts may be bogus and Apple could reveal an entirely new design. However the company has been developing a consistent design across its products - the latest iPod Touch uses a teardrop design, while the new iPad has a thin aluminum body - despite criticisms over poor antenna signal and fragile form factor. A metal back could alleviate the back glass shattering.

What's not known is how Apple will complement the iPhone 5 with iOS 6, which some see as the most important revision of the operating system yet.