I believe you are referring to the seat spring of the chair. http://www.recliner-handles.com/furniture-springs/recliner-and-furniture-seat-springs.html
Visit this link to purchase seat springs in various sizes from 16 inches up to 26 inches long. you will need to measure youre existing spring from side to side for the correct spring.
John at recliner-handles.com, February 2015
