The SilencerCo Velos LBP 5.56 K uses low back-pressure technology to reduce blowback while maintaining impressive sound suppression. Constructed of 3D printed Inconel 625 core fully welded to 17-4 stainless steel modules. Full-auto rated and the most durable suppressor SilencerCo has ever made. Dedicated for .223 REM / 5.56 NATO calibers. Compatible with Charlie accessories, no barrel length restrictions. Ships with ASR Mount, ASR Closed-Tine Flash Hider, Internal Charlie Flash Hider Front Cap. Note: If this product is reflected as in-stock it means it's either physically in-stock or allocated and available (serial number is assigned) at my distributor