Apple has been refreshing its iPhone smartphones yearly. The most recent model was the iPhone 6 and iPhone 6 Plus. This year, Apple is expected to introduce the iPhone 6S and 6S Plus, Fox News reports.

Apple found that more consumers are preferring large-screened phones and increased the size of the iPhone 6 and 6 Plus. Since the upcoming phones are "S" models, little to no external changes are expected to the phones. Instead, the iPhone 6S and 6S Plus is expected to improve its internals.

The brand new Apple Watch was the first device to use Force Touch. Force Touch allows devices to recognize how much pressure is being applied to the screen and respond in different ways according to the amount of pressure applied. The iPhone 6S and 6S Plus will likely be equipped with a new screen that would support Force Touch.

The camera on the iPhone has been improved model-by-model; however the camera has been stuck at 8 megapixels (MP). For the first time in quite a while, the iPhone 6S will be getting a jump in megapixels. Respected analyst Ming-Chi Kuo has predicted that the new camera will be 12 MP. Aside from the megapixel boost, the photo quality of pictures taken on the iPhone 6S are said to be close to DSLR quality.

A brand new processor is expected for the new iPhones. The Apple A9 processor is expected to be faster and more efficient.

Apple has never used more than 1 GB of RAM in its iPhones. For the iPhone 6S, Apple is expected to double the RAM to 2 GB. This will make the device even more powerful and fast.

Stronger materials are expected in the iPhone 6S. The material used on the new iPhones is reportedly the 7000 series aluminum. This would make the iPhones much stronger and durable. Apple uses the 7000 series aluminum in the Apple Watch.

The battery size on the new iPhones is expected to be pretty much the same as in the iPhone 6. However, thanks to improvements in the A9 processor, improvements made to iOS 9 and a brand new low power mode, the battery should last longer in the iPhone 6S.

Leaked images from the French website NowhereElse have shown the stronger materials that the iPhone 6S is expected to use, according to Mac Rumors.

Apple is expected to announce the new iPhones sometime in September.