Greetings, I want to change all 4 speakers but do not know the max size speakers that can fit on it. Also, is there a way of installing tweeters? Thanks in advance...

Standard door pockets at front are 10cm but will accept 12 without any cutting or altering,but you must make sure your replacements are not so deep. I dont remember the standard with rears but most people will place new speakers in the parcel shelf and just cut this to fit.

are you sure about that? Over at coltclub.gr people tell me that the front door speakers can be up to 17cm (6,5 inches). I'm not interested in mounting the rear speakers anywhere else than their proper, factory placing. Can you shed some light on the dimensions that will fit? Thank you very much for the reply.

6.5" will fit front & rear. But you will need to make new door pods for the front. MDF will be fine. Just watch your mounting debth as the window needs to slide behind them!