Way fast. Needs USB-C to Lightning cabling.
You can purchase that cable on eBay. Search item number 331925562353.
I went Apple Store on this. No regrets.
How much fast? the normal adapter takes 5 hours for charging 12.9 from 1 to 100% , what about this one? it means how many hours? Does it hurt your battery?
How much bigger and heavier is the cable?
I'm just about to order it but finally Does it hurt your battery health or not? could be harmful?
One year later with no harm to battery. Still fast charge from 20% in less than 2.5 hours, even faster in iPad 9.7 and iPhone 6s. Battery life is same on all devices lasting more than a day with heavy usage for social, text, email and telephone.