Agree Charlie. The Optum SPS was the same concept, but was heavy to carry acroos the track from the car. I can put 6 isorbics in my bag and barely know they are there. I use them in groups. ESTI has some set up for 20 yd and some 40 yd as is standard. Very beneficial for my players. They come out so much lower they sometimes stumble. They are shocked at how much quicker they fell over first 10.