It's easy to use, safety clip to bring the sides in and have baby feeling snug. It does not make a difference on your body when wearing (even the block insert to keep baby up in position). It keeps baby very warm especially being up against your body, so be sure not to overdress baby in summer.

This is needed for the ergo baby carrier if you want to use it for tiny babies. It is good if you can get it right, it is very tricky to get the baby into the correct position and then get the H2H in the right position but if you get it right it is very comfortable for both the baby and the wearer. I think it is and item that if used often it would become easier but I have not used it that much yet. Due to the fact that it is only needed for a short while I would try find one on ebay or similar as they are likely to be "like new" but cheaper.
Means you can use the ergo baby carrier earlier than without the insert.
Tricky to use.