Cub Cadet SRC621 (12A-997A100) - PartsTree PartsTree - Select Cub Cadet SRC621 (12A-997A100) - Cub Cadet Walk-Behind Mower (2003) Diagrams and order Genuine Cub Cadet Mowers: walk-behind lawn mower Parts. Easy Ordering, Fast Shipping and Great Service!General Assembly · Carburetor · Transmission & Bag Assembly · Control - Equipment Customer Service - Cub Cadet Model Number src 621. Serial Number. See your local Cub Cadet Independent Dealer for warranty details. To ensure the download of the operator's manual specific to your unit, we require a model and serial number. *Based on TraQline data for lawn tractor sales 2014-2016.