We all know what dumbbells look like, right? Usually, they consist of a narrow handle or handgrip in between two weighted spheres or disks. They look sort of like an exaggerated hourglass figure. They're designed to be lifted with one hand rather than two, to add weight and resistance to moves like unilateral bicep curls. They come in a wide variety of weights, from 1 pound on up, but the basic design is the same with one exception ? PowerBlock Adjustable Dumbbells.

The PowerBlocks are a revolutionary design that makes working out with dumbbells an actual pleasure, and lets you have a complete set of free weights that's small enough to store on a bookshelf. Here's how PowerBlocks lets you fit a whole home gym into a milk crate sized space.

Working Out With Conventional Dumbbells

Conventional dumbbells come in a variety of sizes. If you want to work out using different weights for different exercises, you need to buy a set of dumbbells in each size you want. That adds up after a while ? not just in money, but in space needed to store your growing collection.

The solution is a set of adjustable dumbbells. Adjustable dumbbells have a center bar and several sets of weights. The weights slide onto the bar and fasten into place with a locking collar of some sort. The advantage is that they take up much less space. The disadvantage is that you have to take them apart and put them back together every time you want to kick your workout up a notch.

The PowerBlock Difference

PowerBlocks is a complete set of adjustable dumbbells that fit into about the amount of space that a milk crate takes up. Imagine having a full set of dumbbells ? in a milk crate. The real difference, though, is in the way that you adjust the weight on the PowerBlocks. There's no fiddling with wrenches, no sliding weight rings on and off of bars and no chance of the weights sliding off or rattling around loose as you work out. Adjusting the weight is almost as easy as putting them down and picking them up again.

Most adjustable dumbbell sets have a dozen or more pieces. For each dumbbell, you've got a bar, a collar, a pin, and pairs of weights in all the sizes you want. The PowerBlocks dumbbells have just four pieces:

1. The core

An internal handle that weighs five pounds, the core holds the rest of it together. The handle itself is padded and designed to be gripped in one hand.

2. The weight plates

The weight of each PowerBlock is controlled by sets of 5 pound weight plates, connected to each other in pairs. The weight plates are similar to the plates you'll see on adjustable weight machines at the gym. Each set of weight plates adds ten pounds to the five pound core. Add one set, and you've got 15 pound dumbbells. Add two, and you have twenty-five pound dumbbells, all the way up to 85 pounds. What if you want 50 pounds? We'll get to that. Just hang on.

3. The selector pin

Here's the ingenious part of the PowerBlocks. The selector pin is a pair of metal rods that slips between the sides of the weight plates. To make a set of fifteen pound dumbbells, you just slide the selector pin into place beneath the first set of weight plates. Want twenty-five? Slide the selector pin under the second set of weight plates. That's simple enough, but the PowerBlocks folks have made it even simpler ? they color-coded it. Each set of weight plates is colored a different color. A chart that comes with the PowerBlocks lists the weights and colors so you know at a glance where to slip the selector pin if you want 75 pounds.

4. Adder weights

So you want a set of 50 pound dumbbells but the PowerBlocks only increase in ten pound increments? The PowerBlocks folks thought of that, too. Each PowerBlock has a pair of cylinder slots in the core. They're made to hold a pair of silver cylinders called adder weights. The adder weights give you the ability to add weights in increments of 2.5 pounds ? the weight of each adder. That means that you can increase the weight of the PowerBlock from 5 to 7.5 pounds by adding one adder weight, or to ten by adding two. So you want fifty pound dumbbells? Slip both adder weights into their slots, and set the selector pin to 45. Voila! You now have a fifty pound dumbbell.

More PowerBlock Options

You can buy PowerBlock dumbbell systems in seven different sets ranging from the SportBlock (goes from 3 pounds to 21 pounds in 3 pound increments) to the Elite Set 5-130 that lets you go from five pounds to 130 pounds per dumbbell in five OR ten pound increments. With the PowerBlock dumbbell system you can have a full rack of dumbbells in no more space than a milk crate uses. How does that compare to conventional dumbbells or other adjustable dumbbell sets? Take a look:

1 SportBlock 3-21 Total weight: 42 pounds

7 pair's adjustable dumbbells ? 3, 6, 9, 12, 15, 18 and 21 pounds Total weight: 168 pounds

14 fixed dumbbells, 2 each 3, 6, 9, 12, 15, 18 pounds Total weight: 168 pounds

That's a lot of space saving right there. But it really adds up when you look at one of the larger sets. With the Elite 5-130, you've got the equivalent of 37 pairs of dumbbells or 4,820 pounds of free weights in a block that's about the size of a pair of shoe boxes.

Add Barbells to Your PowerBlock

Trainers will tell you that you'll get your best training by alternating between dumbbells and barbells for weight lifting. With PowerBlocks, you don't have to go out and buy a whole new set of weights to have both dumbbells and barbells. Some of the PowerBlock sets can be combined with a special bar that allows you to turn your SportBlock or Personal Block into a set of barbells just as easily as you change the weight ? and they'll still fit on your bookshelf.

But if you want something a little more stylish, you can also purchase an optional stand for the PowerBlock that holds your dumbbells at just the right height for lifting. In addition, several of the sets can be expanded to add more weight by purchasing an add-on kit.

If you're thinking of adding adjustable dumbbells Toy Mould to your home gym, or want to replace the bulky set you own now, the PowerBlock is definitely worth a look.