These machined steel zinc plated extensions thread into the top of the fork in place of the fork cap and add up to 2" of adjustability in fork length. They are perfect for taller riders, taller rear tires or springs, or just for increasing front ride height and adjusting rake and trail.  Easy install. Sold in pairs.
 
Informational video here: https://youtu.be/5d0aM7QHxbU?si=KiJg6I0ndwUwGKEl