If you're installing a Husky 16K roller (HT32220) on 4-bolt base
rails, then you need to install 2 extra bolts in the base rails to
ensure proper performance. This kit includes those bolts, along with
washers, nuts, and spacers. The kit is not needed if you are installing
the roller on 10-bolt base rails.
The center bolt kit is included with the Husky 10 Composite slider and the 10-16 slider.