Here is the information from the packaging: Size Medium: for average or tall & thin body types; possible t-shirt size: S-M
"the sling can be worn five different ways to carry a baby or a toddler up to 36 lbs."
I used the sling with my son when he was a newborn and also as an older baby. By the time he was a toddler, I was pregnant again and didn't use the sling anymore.
Hope this helps. You might also find more info at their website: www.thepeanutshell.com
I will send along the information that originally came with the sling. It includes photos and instructions for three different carrying positions. You can find the same information here: http://www.thepeanutshell.com/Products/Using-Your-Sling