HERE is a link to the hinge types that will make it easier to match up the vent covers to the ones that you have. I would suggest getting the Unbreakable Polycarbonate ones with 5 year Warranty. A few bucks more but they really are worth it. A short video on how it is done is
HERE. MaxxAir vent covers after you have replaced the vent lids is a great idea they will protect that vent lid and you can open the vent when it is raining.