Simplify the following text for a Grade 12 native English-speaking person.
Original: Ltd. , these comprised six different types , all the same size , being 39 f long , 6 f wide , ( 7 f over steps ) and 8 f high -- large by narrow gauge standards -- and certainly superior to any previous British narrow gauge stock .
Simplified: These were of comprised six different types , all the same size , being 39 f long , 6 f wide , ( 7 f over steps ) and 8 f high -- large by narrow gauge standards -- and certainly better than any earlier British narrow gauge stock .