09 Spec b Master Clutch cyl

[Emerson_09specb]

Hi everyone! first time here does anyone know why the spec b mast clutch Cyl is not what you get when you from advanced auto and I ended up having to order STI parts. I know the B is an STI but why are the parts in the system not right? does anyone know? Should I just be ordering STI parts from now on? Disclaimer this is my first SUBIE. Does anyone else have issues finding parts for the Spec b? Or am I Just an idiot? Thank you