I bought these covers to go with Bummis Organic Cotton Prefolds. I bought newborn covers and preemie prefolds and they worked just PERFECT with each other.
My son was 7 weeks early and I wasn't prepared for that - I didn't have cloth diapers that would fit him. When we brought him home he was 6 pounds and these covers fit him great.
The newborn size is from 4-9 pounds and it's true - 9 pounds on the dot and they just were too small. So they fit him for about 8 weeks. It was well worth it, though - I didn't have to fiddle with huge prefolds or covers with snap down rises that would have just been enormous on my little guy.
I will say that the velcro, while it held up beautifully with washing, is a little bit stiff on the larger sizes. The newborn size it's fine, but we also bought one of these covers in size medium and the velcro is just so stiff. It seemed uncomfortable for my son to sit with it on.