The seal rings are in important piece in the blender function. One seals sits in the lid, while the other sits in the base of the blender to ensure there are no messy accidents.
It’s always handy to have some spare seal rings as from time-to-time, they can break or split, meaning your blender might start leaking. An easy way to troubleshoot is to have your spare seal rings at hand, replace the old, and ‘voila’, your blender could be working like new!