Steel Blind Rivet MR40121 – 5⁄16-3⁄8-in Grip Range

The Howmet / Marson MR40121 (your BR4-6SSD code) is an all-steel blind rivet with a nominal body diameter of 1/8-inch and a grip range of 5⁄16-inch to 3⁄8-inch (≈ 0.313-0.375 in). Supplied in bulk (typically 500 per pack), this rivet is built for heavy gauge or thicker material applications where maximum strength is required and only one side is accessible. Originating from Howmet’s Mexican manufacturing, this steel rivet delivers strong shear and tensile performance, making it suitable for structural or heavy-duty assemblies where durability is paramount.