Fabia 2 front, rear door speaker size?

Hi,

does anybody know the size of rear door speakers. When we bought new Fabia 2, we didn't order the extra 4 rear speakers. And now i got my hands on some newish 17cm Pioneer speakers and I am wondering if they would fit. I know that Fabia 1 has 13cm size speakers. My local dealer couldn't tell me the size, but said that they are the samo size as front speakers. Don't get me wrong, but I newer heard a 13 cm speakers that could make so much bass. Fabia 2 Sport has excelent front speakers.