Polini Exhaust. please help!!!!

hi friends 

I have Taiwan vespa 50ss.(some parts from pk some from real 50ss vespa)

this vespa already was with poling 85cc Cylinder.

and now I want to buy Polini exhaust, but can't understand which one I have to buy...No. 20020300 or No. 20020500 ?? u can insert on sip-scooter to check)

and please can anybody explain me difference between this two exhausts)

for earlier thank...friends)