Cage doors?

I'm looking to get my 4 budgies a new cage. I found this one, which I'm hoping is big enough, and I'm almost done with saving up. However, I'm a bit concerned with the doors. The cage I currently have has a big door in the middle with a lock, which is practical and makes it easy for the birds to get out. I'm not sure about these doors, though. They work like a flap, dont come with a lock and the size isn't stated. I know that you can purchase locks seperately, but I still want to know if I should see the sizes and flap design as a deal breaker.