The Knappie Snap one size diapers were one of my first cloth diaper purchases as well. I sold most of them as I got into hemp, but I held on to a couple since the celestial fabric is so cute.
They fit well when we started using them a year ago (about 20 pounds) and still fit with room to grow now at 27 pounds. The snap configuration is unique and you don't have to fold the snaps in at the smaller settings, which is nice. With 3 rise settings, these have a lot of adjustability.
They are pretty trim, but I did need a doubler for heavier wetting times like the morning or naps. They dry very quickly.
The price has gone up considerably since I bought mine at $75/dozen, but I think they are still a good value. These are a great workhorse diaper that have served us well.