Convertible seats when used rear-facing should be used for which of the following?

When using convertible seats in a rear-facing position, it is essential to follow guidelines that ensure the safety of infants. Firstly, convertible seats are designed to accommodate infants less than one year of age and weighing up to about 20 pounds, which is crucial for their safety during travel. This age and weight range is recommended because infants are more vulnerable to injury in a crash, and rear-facing seats provide better protection to their head, neck, and spine.

Additionally, the correct positioning of harness straps is vital for optimal safety. They should be placed at or below the infant's shoulders, allowing for a snug fit that can restrain the infant securely during a collision. Moreover, the harness clip must be positioned at the infant's armpit level. This ensures that the harness is appropriately adjusted to prevent the infant from sliding out or becoming too loose, which could compromise their security in the seat.

The combination of these guidelines works together to provide comprehensive protection for infants in a rear-facing convertible seat, making all of these considerations equally important for safe usage. Therefore, selecting the option that encompasses all these necessary factors is the best choice.