A "hinge fixed pin 3.5x3.5x2mm brushed nickel" refers to a hinge with a fixed pin, measuring 3.5 inches by 3.5 inches with a 2mm thickness, and finished with a brushed nickel coating. The brushed nickel finish provides a muted, matte-like appearance, as opposed to a highly polished one. These hinges are typically used for doors and other applications where a non-removable pin is desired for security or other reasons.