What is Rear facing max?

Rear facing max is the point at which a rear facing seat has been used for as long as it is meant to be used, so it is time to turn the seat forward or move up a stage. Rear facing suits a baby's head and neck better, so a later limit gives you more months of it.

The limits here are given in different units, which is worth noticing. AXKID lists 125 cm and BeSafe lists 125 cm / 22 kg. Britax lists 50 lbs / 49 in rear-facing and Baby Jogger lists 50 lb rear-facing, both in imperial measures. Baby Plus lists 15 months, which is given as an age rather than a measurement.