Baby Jogger City Mini Glider Board:

The Glider Board attaches to the rear axle of your single or double Baby Jogger stroller and provides a space for an older child to ride along. The Glider Board is distance adjustable from the stroller to accommodate taller children, features a non-slip surface and conveniently stows out of the parent's way when not in use. Holds up to 45 lbs.