The Geissele Super Duty MOD1 16" Heavy Barrel Complete Upper Receiver in Distressed Diamond Cut is a premium AR‑15 upper assembly built around a rugged cold hammer forged, chrome‑lined 16in barrel with a .750‑inch gas journal and a 1:7 twist for broad ammunition compatibility and enhanced heat capacity. Featuring a mid‑length gas system with a Super Compact gas block and an MK16 M‑LOK free‑float rail, this upper is optics‑ready with a full Picatinny rail for sights and accessories. Designed to mate with any compatible AR‑15 lower, the 08‑627S provides the core high‑performance components for a durable, precision‑oriented rifle build. Sold without BCG and charging handle, the complete upper simplifies assembly of your custom rifle while delivering top‑tier Geissele engineering and finish quality.