SON 28 is a hub dynamo universally approved for all wheel sizes from 16″ to 29″. The rated output is achieved in the 700c (622)-wheel at approx. 16 km/h (SONdelux at 19 km/h). Thus, SON 28 is recommended if a lot of light is required at low speed or when either devices are to be operated or their batteries charged.
At last: a hub dynamo for suspension forks with 15 mm thru axle. SON 28 15 disc corresponds to SON 28 disc 6-hole in every other respect.