This premium XL-type synchronous timing belt pulley is precision-machined from high-grade aluminum alloy, featuring 40 teeth designed for standard drive belts. Engineered for precise mechanical motion control, it has a 5mm inside diameter bore tailored for NEMA 17 stepper motor shafts or matching rotary rods. With an outer diameter of 40.5mm, an 18mm total width, and dual integrated M4/M5 threaded grub screw holes for secure locking, this durable gear delivers zero-slip power transmission, making it ideal for DIY CNC routers, 3D printers, linear actuators, and custom robotics projects.