My set of nice platform peddles are 9/16 , the Electra 1/2"
the
1/2" comes on One Piece cranks there is the pedal extender . male 1/2"thd , Female 9/16"thd..
http://www.kneesaver.net/ecommerce/s...-adaptors.html
since many stationary bikes use OPC , these let you use any pedal [that does not mount only by the end of the axle]