The First Years True Fit si C680 Instruction Manual page 8

Section 4 - Use Recommendations
C680 True Fit si Convertible Seat Rear Facing
Use Requirements:
This child restraint, with the upper seatback installed in a
rear facing position, is designed for use by children whose:
- Weight is between 5 and 35 lbs (2,3 and 15,88 kg), and
- Head is 1 inch below the top of the seat.
Child MUST meet BOTH of these requirements to use this
Convertible Seat.
1"

7
Max
Head
Height
5 - 35 lbs
Rear Facing
Use