glock-slide-assembly-exploded-view-parts.jpg

The Glock slide firing pin channel has a part installed in it which is called the channel liner. ... The purpose of the channel liner is to lessen the firing pin spring and spring cup wear and to eliminate the need for lubricant.
https://www.rockyourglock.com/custom/JCLT.htm
https://www.rockyourglock.com/parts/...annelLiner.htm

Do rock slides come with channel liner?
Answer: The slide will come with a channel liner if the Internal upper parts kit is purchased at the same time.