The Tactical Solutions PAC-LITE IV� upgrade is designed to replace your factory Ruger� Mark IV� or Mark IV� 22/45� upper to reduce weight increase accuracy and improve reliability. This upgrade is easily installed and is offered in 4.5� and 6� barrel lengths. Available in Gun Metal Gray Matte Black and Matte Olive Drab. The improved balance and accuracy of the Pac-Lite makes shooters feel like a pro. Installation on your existing MK frame is a cinch without the need of a gunsmith. - Specs: - Rate of Twist - 1:16� - �� x 28 Threads - 11 Degree Target Crown - Stainless steel Breech face and receiver - Lightweight Aluminum Barrel and receiver - Weight: 9.5oz - Length: 6� - Matte OD Green Fluted