SON Rear Light for seatpost mount

What comes to hub dynamo powered rear lights, it does not get much better than this. 

• For seatposts-ø 26 up to 31.8 mm

• SON Coaxial Cable 190 cm (fixed inside the housing, bare ends, connectors separately enclosed)

• Conforms with German legal regulations / ISO 6742

• Weight (w/o cable): 35 gFor 6 Volt alternating current (hub dynamos)