The Nuna PIPA Series Insert can be used as necessary to provide a snug fit for small babies in the Nuna PIPA, PIPA RX, PIPA Lite, PIPA Lite R and PIPA Lite LX. The low birth weight pillow can be used in the infant insert for even smaller babies, but should be removed once a snug fit can be achieved without it, at approximately 11 pounds. *Not compatible with Nuna PIPA Lite RX models