Bilstein install question



Its E4-RO1-Z008A29 - 12 x 10.2 x 38.5 Sleeve for the rear shock upper stem.

Anyone has any idea if this is really needed and if I could reuse existing ones, assuming there are existing ones in OEM setup.
I don't want to go to the shop and have them find out they need these sleeves half way threw the install.
Thanks
Darius



