Kerastase chronologiste line is a luxury line.This is the best price for this set. This is a never used pack of 4.. this line is more expensive then other keratase lines because of its purpose. its a luxury scented and moisture line primarily used in the winter for dry hair/scalp that needs a boost of moisture and repair. it is recommended to be used once every 2 weeks. the serum is a perfume scented serum to give your hair that luxury long lasting shine and smell!