We bought our Graco Duo tandem for when our littlest bubba arrived and were slightly disappointed to find that it didn't come with a rain cover. Living in this country a rain cover is pretty essential if you don't want your little treasures to end up completely soaked during a shopping trip.
You can come across cheap rain covers in most places, I've even seen them in the pound shop but unfortunately they're not long enough to cover both seats on our tandem and so we had to buy the official Graco version which cost a lot more! We bought ours from Amazon for £15.
The raincover doesn't come with instructions and it really isn't as self explanatory as you'd think to attach it! However once you have figured out what to do with the elastic ties it really is relatively easy to attach to the pram. It doesn't take long to put it on which is a massive plus when you're struggling in the rain! However it is quite difficult to fold down to take out with you "just in case" and I've found I have to carry it in a separate bag when we go out - not ideal when you're already carrying half your house with you in your changing bag! Having said that, you would expect the cover to be quite large with the amount of space it needs to cover.
Once it is properly attached it stays in place thanks to the elastic ties and good quality plastic. It doesn't flap around in the wind and it stays secure without the worry that you'll end up chasing it down the street.
The plastic is quite thick and seems a much better quality than the cheaper versions that are available. It keeps my little ones dry when it's on, and does what it says on the tin. However I do have a complaint! Due to the nature of the pushchair, the newborn or smallest child, sits at the back. If our little one begins to cry we can't get at him when the rain cover is one without taking the whole thing off. This means that both the baby and the toddler get drenched and then we have to reattach it! It would be ideal if there was a fastening at the back so we could reach the baby without having to disturb the toddler at the front.
This raincover does the job, but could be a lot handier with a way of accessing the baby at the back.