* Hello Cedric. The size 4 Premium nappies (windeln) have the indicator strip that turns blue when wet so you can see if they need changing without removing the nappy. They are also slightly more flexible for daytime use when crawling or walking. Baby Dry nappies are otherwise identical and are also very good.
* The 4+ nappies are for the same size child but are thicker and more absorbant for nightime wear or long journeys, but are only available in Baby Dry not Premium (so no indicator strip, less flexible)
* So basically choose the size 1, 2, 3, 4, 5... according to your child's weight and either Premium or Baby Dry for the daytimes, then Baby Dry + size for night or long journeys)/ diarrhoea when you won't be able to change the nappy so often or need extra absorbsion