I think thay are 5 1/4 speakers.I changed my out in my 4 slot to Polk car audio speakers cause I had some from a car I had and they were the right size and ohms.DarkHuman said:yay! So i guess my only other question is: What size speakers do i need (and how much juice can i give em?!)---or how strong is strong enough (and how strong is too strong)