Griffin Armament Primo Gas Block low pro. 750 inch. ID block made from nitrided 416R crucible alloy steel. The block has two provisions for mounting set screws and / or pinning. The included splined pin allows qualified gunsmiths and experienced builders the option of having a military style secured gas block. A 1/8 inch carbide drill bit and three ton press are recommended for pinning. Knurl grip cup pointed fasteners ensure a secure attachment to host barrel. The PRIMOs pre-drilled hole helps locate the drilling operation on pre-dimpled barrels for fixture free installation. 416R Crucible Alloy Steel. QPQ Nitride finish. .750 inch gas block diameter compatible. Low profile design. Included splined pin. Knurl grip - cup pointed fasteners. Inlcuded hex key. Included gas tube roll pin. Pre-drilled for ease of barrel pin installation. Specifications for Griffin Armament Primo Gas Block 416R Crucible Alloy: Manufacturer: Griffin Armament Fabric/Material: 416 Crucible Alloy Steel Gas Block Journal Size-Diameter: .750 in Condition: New Package Contents: Griffin Armament Primo Gas Block 416R Crucible Alloy Griffin Armament GAPGB: Primo Gas Block (low pro)