Brake adapter - Post to post
Post-to-Post brake adapters are for mounting Post type disc calipers to Post type frames/forks. The adapters come in both +20mm and +43mm sizes. Each adapter comes with 2x flat washers and 2x bolts.
Are you increasing your rotor from 160mm to 180mm? Get a +20mm adapter. How about increasing your rotor from 160mm to 203mm? Get a +43mm adapter. If you are taking a 180mm rotor fork (like a pike) to a 203mm rotor, get a +23mm adapter.