Product Description The SM-DH10A overvoltage protector by Shimano - keeps the voltage constant The is included with all 6 Volt/3 Watt dynamo hubs by Shimano, but it is also available as a spare part. It ensures that the voltage remains constant and does not become too high. The SM-DH10A must be mounted on the rear light and is compatible with racks with 80 mm hole spacing as well as with 50 mm hole spacing. Specifications:Bolt Spacing:50 mm / 80 mmManufacturer Number:A-SMDH10A Contents:1 x Shimano SM-DH10 overvoltage protector Manufacturer: Shimano Europe B.V. High Tech Campus 92 5656 AG Eindhoven Netherlands info@shimano-eu.com