Convertible Carseats

convertible
capable of being exchanged for or replaced by something of equal value; "convertible securities"
(of currency) Able to be converted into other forms, esp. into gold or US dollars
a corporate security (usually bonds or preferred stock) that can be exchanged for another form of security (usually common stock)
Able to be changed in form, function, or character
a car that has top that can be folded or removed
(of a car) Having a folding or detachable roof