Swytch bike hub wheel is disc brake ready. So, I bought one of 185mm disks. I also needed to buy one caliper for the conversion.
My trike is not ready for the disc brake. So, it does not have ears for disc brake caliper. To mount that caliper, mounting bracket is needed. It is important to know the size/diameter of your bike’s fork. This bracket usually comes with two sizes, 22 mm or 31.8 mm.