What is the opening for at the back of the Purebaby Sleeping bags?Updated a month ago

It is designed for when taking your baby out and about – It’s a seat belt/restraint slot on the back and it is another great benefit of a Purebaby sleeping bag, allowing you to safely move your little one from a pram, to their cot/sleep space without the need to remove the sleeping bag them when fastening and un-fastening seat belts/restraints.