Each zip file contains several mp3’s of the same passage at different speeds.
169 United Credit Bureau
170 Christmas gift, Album of the Month Club
171 Mrs. Young, if you are unable to shop
172 Doctors and ministers must have strong tires
File names are in the format: gsf2-13-110-40-90.zip
gsf2 = Gregg Simplified Functional 2nd Edition
-13 = Lesson 13
-110 = passage 110
-40-90 = speeds from 40-90 wpm in 10wpm increments.
See this post for more info: