The optional Seat Depth Extension adds an additional 5" of seat depth.

Please Note: If you are purchasing a Seat Depth Extender for a Thomashilfen Booster Seat that you already own, please call Customer Service at (800) 371-2778 to discuss retro fitting adapter plate required for older models of the booster seat. 

Please Note: Seat Depth Extender and Footrest CANNOT be used in combination.