Boomstick FC-I Barrel Back - Forged Carbon FiberDye continues to be the leading innovator when it comes to barrel systems, and the new FC I (Forged Carbon Insert) barrel back is the newest creation from the mad scientists at Dye. The first of it's kind, the FC I barrel back is forged carbon fiber barrel back that is compatible with UL I barrel fronts only, and utilizes Eclipse PWR inserts (or any other PWR compatible inserts) for ultimate accuracy and performance. Dye Boomstick FC I Barrel Insert