They have little elements built in which allow you to just hose the nappie down without removing it from the baby and the miniature solar panels dry it almost immediatey. p.s. For those mums who do not have access to a hosepipe the same result can be obtained by sitting baby in lukewarm water and moving lightly to and fro, whilst singing Be Baw Babbity. To e-mail customers, the Mark 1 version of this product is not now in production, as babies were having difficulties dragging heavy electrical cables over the floor.