Organic cotton baby gown is great for infants. Keeps baby feeling snug as they did in the womb. Baby gowns also allow babys legs to have skin to skin contact which studies show is great for infants. One size fits babies and newborns from birth to about 6 months. 
As a parent, I love to save money, so I cut out the bottom when my baby grew to allow them to wear the gown longer.