The new diesel barrels have a longer control bore and stronger tip to prevent fraying and tip damage and new graphics. Tyson from SLY says..
“A re-enforced carbon tip ensures durability without adding unnecessary weight. The six inch back adapters have been implemented tosuit the traditional crowd who generally prefer the longer control bore, and of course we still use the Dual-Carbon technology allowing the player to shoot through broken paint.”
Apparently they are available now through Sly direct and you can check them out at worldcup.