Purity: Material of the Jabirah Splint
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 330:
It is not necessary for the jabīrah to be made of something that one is permitted to wear when performing prayers. Therefore, if the jabīrah is made of silk or pure parts of an animal whose meat is unlawful to eat, it is permitted to wipe over it.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)