Add-on lenses for iphone camera?

I see ads for these lens sets, but it's usually not obvious how they attach. One ad mentioned magnets, but I don't think there's any steel in my Iphone 5.
I'd appreciate hearing from anyone who has a set for there iphone 5.

Iphone camera is just unbeatable, have a look at different iphones here http://newbestmobiles.com/category/apple/

https://www.uniquephoto.com/carry-and-support/ipro-lens-system-case-for-iphone-4-4s-0ip-case-ip4/?scid=scplp7232827

These go on your iPhone easily or they are on a case