Have a Colby carpet,red river and a killer spinner, they each have there place! For me I like chain pulls /sprints over the carpet,my bike over the killer spinner and hill climbing / sprints over the red river! Don't get me wrong I use all three but if given the chance to get wind in my face and dirt under my feet I'm gone see ya in about two-three hour's! :-) plus I can feel if my buddy is not fully recovered from the workouts from yesterday. Do llike them during clean up place one on each mills and get those three spots fresh and clean while they burn off some steam!