Highly efficient super light weight premium grade 6 volt 3 watt dynamo front hub with easy to use quick release the shimano nexus 3n80 6v 30w qr dynamo front hub provides bright illumination for safer night riding without the need and expense of replacing batteries important weight savings are made by using an efficient and light weight aluminium coil structure labyrinth and contact sealing as used on the premium dura ace and xtr groupsets low friction seals and internal grease sleeve ef