JARD Bolt Action Knob Fat Ribbed Outer Diameter 0.875in Length 1.5in 5/16x29 Aluminum Black. All our knobs feature 5/16-24 thread pitch - The industry standard. All of our knobs are machined aircraft grade billet aluminum for a lightweight feel and anodized for a clean polished finish. Specifications for JARD Bolt Action Knob: Manufacturer: JARD Fabric/Material: Aluminum Color: Black Package Contents: JARD Bolt Action Knob JARD 4827: Bolt Action Knob Fat Ribbed Outer Diameter 0.875in Length 1.5in 5/16x29 Aluminum Black