The only dumbbell system that can expand to meet your strength needs, PowerBlock dumbbells are the most versatile and effective exercise tool ever developed for strength training. PowerBlocks work intuitively. Rather than requiring you to buy a room full of dumbbells, PowerBlocks act just like a weight stack at the gym, with a weight handle that fits inside the first weight, which fits inside the second, which fits inside the third, etc.

When you want to change weights, you simply move the weight selector pin into the appropriate slot and you’re set. As you lift the core, all the weights above the selector pin are lifted at the same time, turning your 3-pound dumbbell into a 6-pound dumbbell, or your 6-pound dumbbell into a 12-pound dumbbell. Not only is the system remarkably easy to use, but it’s also cost- and space-efficient, as a single pair of dumbbells can do the work of dozens.

This pair of 45×5 dumbbells, for instance, adjusts from 5 to 45 pounds in 5-pound increments (5, 10, 15, 20, 25, 30, 35, 40, and 45 pounds), in effect doing the job of 18 individual weights. Even better, the weights are more compact and balanced than traditional dumbbells, with a padded handle that protects people with weak wrists. Best of all, the free weights are terrific whether you’re trying to build muscle mass, firm and tone your physique, or get rid of unwanted body fat. The adjustable set offers a maximum weight of 45 pounds per hand and carries a limited 10-year warranty.