Britax safe-n-sound BS0072E-i20133 Instructions For Installation & Use page 20

IMPORTANT: Follow this advice.
Marker A: LOWER SHOULDER HEIGHT MARKER
When the child's shoulders reach
the lower marker, the child restraint
may be turned to face towards
the front of the vehicle Britax
recommends to maintain rearward
facing while the infant can be
accommodated comfortably or until
the shoulders reach marker B.
At least 12 months of age.
Marker B: MIDDLE SHOULDER HEIGHT MARKER
When the child's shoulders reach
this marker, the seat must be
converted into forward facing
mode.
Approximately 2 to 3 years of age.
Marker C: UPPER SHOULDER HEIGHT MARKER
When the child's shoulders reach
this upper marker, the child is now
too big for the child restraint. It is
now time to move to the next child
restraint type.
Approximately 4 years of age.
This child restraint is unsuitable for an occupant whose shoulders are above the upper height marker. The
child needs to be moved into the next form of child restraint.
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Instructions for Installation & Use