Some barrels do not need a sleeve, I checked my Prophet 25 and 177 barrel , NO sleeve needed , Same with my Uragan , Mutant and old school bull pup 22 Cricket,,, Now I have read that some brands have thin wall barrels and could be helped with Carbon fiber sleeves , Its called barrel tuning as the barrel flexes up and down as the pellet is shot through the barrel,,, The only way to make these barrels flex is to bang on the end with a sledge hammer. Now I got the carbon fiber foo foo wrap on my shrouds just for bling and keep the finger prints off, I think it looks cool,,,, To each his own I guess .
Mike