Good mix of speed and speed endurance. I used to always start my season with se 300s. I once got down to a 35 sec 300. That year I ran 10.3. I just think that in the last 2 seasons my endurance has dropped. I plan on doing 6-7x300 tempo sessions in gpp and 2-3x300 during spp for se workouts. I have never been one for endurance but i could run the hell out a 300. I can barley run 150 right now.