Simplify the following text for a Grade 11 native English-speaking person.
Original: The Class 221 SuperVoyagers are similar to the Class 220 Voyager units , but they are built with a tilting mechanism offering up to six degrees of tilt to allow faster speeds on curved tracks .
Simplified: The Class 221 are similar to the Class 220 Voyager units , but they have a tilting mechanism enabling up to six degrees of tilt to allow higher speeds on curved tracks .