Cylinder of model Breitwand which is simply called sun spring in Sweden.
Made of aluminuim with nicasil coating.
Standard 39mm bore which gives 50cc and delivers about 5.2hp.
Corresponds to Zundapp original number 284-02.708
Exhaust nozzle 36mm.
CC intake 45mm, M6 thread for studs (not included)
Pay attention so the pin for the piston ring is mounted against the intake and not the exhaust port.