Vkworld F1 is an old model from Jan, 2016. It has a 4.5-inch small screen, which is very unusual in today’s market. Almost all smartphones today are over 5 inches. But there are still some people who need smaller phones. And most of these people are the elderly. That is why vkworld starts to resell F1 and this time they are going to add lots of features that make F1 a smartphone for the elderly.
Firstly, to make the UI easier to look at, the font size is 5 times bigger than normal size. And also vkworld designs a new UI with much bigger icons and simpler functions. Therefore, old people don’t have to spend lot of time finding what they what. And the functions of the phone is just as easy as feature phones. But you can still access to the internet and use smartphone apps.

And vkworld also chooses a much louder speaker to take care of people with bad hearing. The phone will automatically read the phone number out when you receive or make a phone call.

Moreover, there is built-in SOS emergency call on the desktop. When you are in danger, you can enter SOS function and activate the SOS emergency ringtone. And also you can make SOS phone call for help. This is very useful for the elderly when they are in danger.

However, if you don't like this UI, you can still turn it off and use regular Android UI.
More detail: http://www.vkworld.cc/product/5a336cd6e6473