one nappies have a waterproof cover built into the absorbent
all in ones generally use
laminated PUL polyester for the waterproof outer which may be smooth or topped with velvety minky or cotton
most all in ones are lined with a stay dry polyester fabric against the skin
the advantage to this system is convenience while the down side to all in one style nappies is their increased drying time + cost
factor of changing a whole nappy rather than replacing inserts
these disadvantages have been minimised by the innovation of all in
all in twos have removable absorbent inners
removing the inner
reduces drying time + means that you can buy more 'inners' and less 'outers'
to reduce costs + consumption.