crf bend

can i pick any pipe within size rang for my pitpro se 125 or do i just have to get another stock one the one on it the previous owner clearly didnt look after the bike or own a shed so need a new only because it makes it look so horrible. Cheers.

just wondering if its a good idea to get a custom made exhaust? ive got someone that is willing to make one pretty cheap he works at a shop that does Car exhausts but has done a exhaust for his 450 and a few other bikes here and there , this is for my crf50 with 88cc s stage kit , what size pipe...