Denim stitching thread is a type of thread specifically designed for use in sewing denim fabric, which is known for its durability and toughness. Denim stitching thread is usually made of a blend of cotton and polyester fibers to provide strength, flexibility, and durability.Denim stitching thread comes in various thicknesses, colors, and finishes. The most common thicknesses used for denim stitching thread are 30/3, 40/3, and 50/3, with the first number indicating the thickness of the thread and the second number representing the number of plies or strands of thread.