Rifled Choke Tube. Made specifically for big game, target and silhouette shooting! Stainless steel construction with black oxide coating. Precise, twist rifling grooves spin and stabilize slugs for increased accuracy. Rate of twist: 1 in 35" right hand twist with 8 grooves. Extended. Fits Winchoke, Browning Standard Invector, Mossberg, Ruger, Savage and Weatherby in 20 Gauge ONLY. Included choke tube key for easy installation and removal.