Hello. Can't find a tape measure but we have a small for Talia who is 3 months old and it fits and still has a good month or so of use out of it. SHe is about 13lb now so not small. Soy is the nicest material, really absorbant and soft. I would get the extra booster but I have heavy wetters. They sell on well so I doubt it will cost you much once you sell it on.
Thanks Jenny, it sounds like it will be rather too big for him at the moment then if your 3 month old still has a months use left in it lol (he's 3 months old too but only 6lb 9oz!) but I've ordered him an aplix one anyway on the offchance it might adjust down small enough to fit and if not then he can grow into it. I've gone for soy nappy with the additional night booster being bamboo. Ooooo I can't wait for it to arrive next month
I honestly think a small will fit fine by the time it arrives. I was wrong about Talia having a month left. I think she only has one or 2 more uses and it will be too small! The mediums fit fine now anyway - she is in one now!