The REV Robotics #25 15 tooth sprocket fits on a 5mm hex shaft. The hex shaft interface completely eliminates the need for expensive hubs or using potentially unreliable set screws. Sprockets 15 tooth and larger have a hole pattern on an 8mm pitch enabling easy mounting directly to REV Extrusion, REV Brackets, and other 8mm pitch systems. All REV motion products have a uniform 15mm width to make quick design swaps fast and easy.