A shotgun magazine tube extension: a steel tube with a knurled collar that screws onto the host tube, three barrel bands and an end cap. Dimensions 0.035 x 0.034 x 0.214 m (X x Y x Z). Origin at the footprint centre resting on y = 0; the mount port is the threaded end that screws onto the host tube; metre units, +Y up, muzzle and point toward +Z. Connectors: mount magazine at (0, 0.0172, -0.107) facing +Y. Fits a host weapon by laying its mount port on a socket of the same type; the port sits on the mating face, so the two solids meet without interpenetrating. Static attachment with no moving part. Static geometry: no rig or animation. Blued gunmetal, bright machined steel, dark anodised alloy, black and dark earth polymer, rubber, walnut, brass, copper, leather, olive paint, optical glass, concrete and emissive red, green and warm white for reticles, lasers, tritium and lamps. Physically based flat colours with no texture maps. Original invented design: no real make, model, manufacturer or marking is represented. Free 3D model for Unity, Godot, Unreal, three.js and Blender. No collision or navigation data.