Size 4 and 4+

[cairnterrier]

Was just wondering what the point of a size 4 and size 4+ nappy was? As far as I can see, the only difference seems to be in the weight range, but then why would you not just go up to a size 5?

Sorry for ultimately pointless question but finding it difficult to sleep at present hence random musings.

While we're on pointless questions, is anyone else out there eating chocolate not sleeping at the moment?

Think its got something to do with the width of the nappy so a chunkyish baby thats not quite ready for a size 5 can have an inbetween but been using washables so long i cant remember the difference :s