Question on Walton’s Fibrous Casings ***

First time on Walton web site.
I enjoy all your videos and have learned an awful lot.
One question that I do have.
Are All your fibrous casing protein lined??
Your web site does not state if they are or are not.Also what does PRE-STUCK mean that is also listed on the description on fibrous casings.
I was interested in the 1.5" fibrous casing to make dry cured sausage, and the 2.4 salami casing to make soppresata, I know some fibrous casing s are not protein lined.
NOTE: I WILL NOT BE cooking or smoking these casings.
Stuffing them and hanging them in a dry cure chamber I appreciate your help. Thanks

Thank you Jonathon and Glen, your information was very helpful.