These are my main stash filler. My 7 month old son is 10kg with a tiny waste and big thighs; the two row side snaps and the elastic around the tummy make sure there is no gaping. Ensuring a perfect fit nearly every time. The insert are tri-folding, so dry really quickly and are great in winter.
They can be a little fiddly to get on if your not used to side snaps, but are worth the effort.