The Eclipse/Lapco RIFLED PWR Inserts are designed specifically to work with First Strike rounds. Its heavily chamfered breech-end opening and stabilizing collars help eliminate FSR fractures in the barrel. Rifled for accuracy. Threaded for security. Engineered to perfection. The Rifled PWR Insert incorporates a unique threaded section which secures the insert into the tactical back section and prevents rotational movement when the FSR is fired. This creates a stable environment for a more consistent and accurate shot.Available in two bore sizes, 0.686” and 0.683”, these precision-machined rifled inserts allow the player to accurately match the rifled bore with the batch of First Strike Rounds for supreme performance. Features: Eclipse Rifled PWR Insert Manufactured in the USA by Lapco 8.5” Length 0.686” and 0.683” Bore Sizes Available Threaded Locking System PWR Insert available in black only Composition Aluminum