Allen Engineering AEM4-65 (Black). Designed for 6mm and 6.5mm calibers including 6mm ARC, 6mm MAX, 6.5 Grendel, and 6.5 Creedmoor. Shorter B-length mount accommodates short-dwell barrels. Internal treatments matched to .30 cal suppressors for extended service life. Length: 8.4". Weight: 20oz. Recommended barrel clearance: 2.2". Mount length: 2.05". 7-10 turns for best fitment. 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