They are loose in the barrel shroud. Not worth the money.
It doesn't need to fit tight in the shroud. The carbon liner sleeve is meant to have a close tolerance slip fit over the liner and add stiffness to the liner and prevent the liner from buckling under compression when you tighten the liner lock at the muzzle. It doesn't need to contact the shroud to do this, the carbon is plenty stiff to do the job and only leaves about .125" of the liner exposed at both the muzzle and breech liner locks.
Previously, this liner stiffening job fell to the o rings between the liner and shroud, which relied on the stiffness of the shroud and contact between the o rings over the liner contacting the shroud to keep the liner from buckling when tightening the liner lock. That reduces liner buckling, but it can still do so between the o rings.
Given manufacturing tolerances on both the liner, shroud, and carbon sleeve, it's never going to be a perfect fit on all 3 components and there will always be clearance somewhere.
There is a noticable reduction in liner distortion / buckling with the carbon sleeve installed. With just the o rings between the liner and shroud, you could rotate the liner lock by fingertip until it contacted the liner and then crank it down with a wrench quite a bit and it would never really feel tight; that was the liner buckling between the o rings. It feels this way even with 7 o rings installed on the liner. Better than 3 o-rings, but tightening the liner lock is still somewhat "springy" feeling where the resistance increases as you tighten but it never feels like it hits a wall and stops.
With the carbon sleeve installed the liner lock actually gets tight and does so very rapidly, because the carbon sleeve stiffens the liner considerably and substantially reduces the buckling under compression. With the carbon sleeve the "springy" feeling when tightening the liner lock is now gone and it feels like it hits a solid wall about 1/16 turn after it contacts the liner. More importantly, I did notice groups at 100y+ tightened up some. Not dramatically better, but enough to notice. My rifle was well tuned before adding the carbon sleeve, but I've heard reports if you're starting fresh the carbon liner sleeve makes the tuning windows wider and easier to find and maintain.
