FX's innovative liner system allows the internal liners to be exchanged for other types.
This STX Superior Heavy liner has a special twist rate that is well suited for heavier pellets and slugs.

Smooth Twist X liners
This FX Superior STX Liner Heavy is the successor to the extremely successful FX STX Slug Liner A.
As with the original STX (Smooth Twist X) liner, the rifling is pressed in from the outside, resulting in a very smooth finish and therefore minimal frictional resistance.

The process has been optimized and some minor changes have been made, achieving even greater precision, resulting in even tighter tolerances with the end result being even greater precision.

The Liner System
The advantage of using liners is that you can easily change caliber or pitch in the FX STX barrel system.
This means that an upgrade such as this Superior STX liner can also be used in your FX STX barrel without adjustments.