After the rail merger, there are three different fare classes on the MTR: Adult, Students and Concessionary. Only children below the age of 12 and senior citizens 65 years or older are eligible for the concessionary rate on all lines. Full-time Hong Kong students between the ages of 12 and 25 qualify for the concessionary rate using a personalized Octopus Card on all lines except on Airport Express, or travel to or from cross-border stations (Lo Wu/Lok Ma Chau). Children below the age of 3 travel free (unless they exceed the height range).