This Adaptor is designed to be used for "post" type disc brake calipers to be mounted to post mount forks/frames. So, if you're looking for a +20mm post to post mount adaptor this is what you need.
The adaptor will allow you to run 180mm rotors on frames/forks that were originally designed as 160mm. It will also allow you to run 200mm rotors on frames/forks that were originally designed as 180mm and so on. If you want to increase your disc brake rotor size by 20mm, this is what you need.
Compatible with all major brands of brake caliper and rotor!