This is the original Thirsties waterproof nappy cover.
The XS small size is the only wrap I've found with an umbilical cut out area.
|Size||Weight Range||Age Range|
|newborn-preemie||4-10 lbs (2-4.5 kg)||0-1 month|
|x-small||6-12 lbs (3-5.5 kg)||0-3 months|
|small||12-18 lbs (5.5-8 kg)||3-9 months|
|medium||18-28 lbs (8-12.5 kg)||9-30 months|
|large||28-40 lbs (12.5-18 kg)||30-42 months|