Apple's iPhone 6 may come in two size variations, yet more rumours suggest. They could also come with super-strong sapphire crystal protected displays to keep scratches at bay. But it's more likely this expensive protective material will appear on the iWatch first.

The latest rumour to suggest two versions of the iPhone 6 comes from the South China Morning Post which claims an insider has revealed details. There should be a 4.7-inch iPhone 6 and a 5.5-inch model due for release in September.

The insider, who claims to have seen prototypes, says the new display will feature a resolution of 441ppi, the same as the Samsung Galaxy S4 and a big jump from Apple's current 326ppi effort.

READ: iPhone 6 with 4.7-inch screen due in June, 5.7-inch iPhone to follow later?

Both phones that have been seen were covered in sapphire crystal glass which is highly resistant to scratches. In fact it's the second-hardest material on the planet after diamond. This material is commonly used on smartphone camera lenses. Never wondered why you don't get a scratch on your camera despite putting the phone that-side-down all the time?

But while multiple sources agree there are iPhone 6 prototypes with sapphire crystal screens, these might not make it to the public. Production costs would be huge and it's more likely this protection will appear on the smaller iWatch displays.

The insider source claims that Apple will do away with the current iPhone 5C but keep the 5S as the more affordable option. It also claims the screen will remain flat, despite rumours of a curved display.

The final design of the iPhone 6 should be reached by April. Expect plenty more leaks around then.

READ: Apple iPhone 6 release date, rumours and everything you need to know