Car Seats and Height

[CeciC]

Does someone know when is the reccommended height for a kid to use a booster seat?

It is weight rather than height that si sued as a definition. Do you mean a highback seat or just a booster cushion ?

this gives a guide to the weights for different groups of car seats.

this gives the law on when (age/height) and where to use the car seats.

Thanks very much for the information.
I meant the booster cushion, well just the booster part of a type 3 car seat.