There are plenty of reasons that if there are a built-in telephoto lens in your phone, why you still need an
external 3x Telephoto Lens?
1. the built-in lens may just got 2X zoomed
2. this added on 3X lens will have better image
3. with the 3x attachment kit (say, a cover or a clip), you can have more different lenses for stunning pictures.
with an iPhone cover:
with an iphone cover:
4. when you take pic of portrait, you will need one.
The picture source:
https://www.pexels.com/photo/woman-smiling-while-wearing-blue-tank-top-160911/
We have many different covers for iPhone for this lens and also universal clip for other smartphones. Don't miss to have a look.
Here is the link to the telephoto lens:
https://dckina.com/index.php?main_page=product_info&cPath=6&products_id=2375