Black Iron Strength® Adjustable Dumbbells Poles Apart® are a patented revolutionary technology because it provides the convenience of 40 pairs of commercial dumbbells in 12 sq. feet, making this unit space efficient. Unlike other adjustable dumbbells on the market, Black Iron Strength Adjustable Dumbbells are the only commercial grade adjustable dumbbells. It an ideal system for the serious lifter. That is why these units are found in commercial and athletic facilities throughout the world as well as home gyms.