Not sure why this can't be answered directly on here. It's a ride height sensor for the DDC. It allows independent comp and rebound adjustment. HP4 comes with a sensor on the shock but not the fork. It may do some other stuff, but most HP4 owners install it for front comp and rebound adjustment.
Not sure if it will be the same on the 2015 with DDC.
All emails have been replied to and all orders have been shipped out.
I still have a good amount of sensors on the shelf ready to go to there new homes. For those of you that are not aware. I am doing the 2D Leveling kits for $530.00 along with free shipping and no tax on orders shipping out of New Jersey.