Lightening holes to save weight.
Inner smaller lightening holes could be used to bolt to pulley that does not have bolt holes is 14mm wide in 4 places radially from centre.
Area available to drill 4 bolt holes if required to bolt to pulley.
Can be easily welded, drilled and bolted to mount on to pulley or wherever required on the engine.
Other sizes available or bespoke custom designs / features can be added please email for details