Question on my slave cylinder

I was getting ready to order the USP metal slave when I noticed the slave on my car isn’t plastic like the factory ones…

I can’t seem to figure out why my slave looks so much different than oem or the usp one.

Mine:

http://i66.tinypic.com/t5i2p5.jpg

oem:

https://jhmotorsports.com/shop/catalog/images/B6_S4_EARLY_Clutch_Slave_Cylinder.jpg