The slides are 22” long but can be cut to length if needed. The cabinet member is typically left 1/2” longer than the drawer member, and both are included. In some cases, you can simplify installation by using the Rear Mounting Bracket for Wood Center Mount Drawer Slide (#56554, sold separately).
https://www.amazon.com/Classic-Center-Mount-Drawer-Slide-4-Pack/dp/B07D3X1ZXT