Flabby arms is one of the many concerns for women who wish to stay fit. The makers of shake weight claim that the device is better than dumbbells and it is designed to help the users develop lean, sculpted arms and shoulders, and toned upper body. According to them, the working principle of the device is based on a workout technology system called Dynamic Inertia. This system is known to work the muscles of the arms, shoulders, and chest in a constantly engaging fashion. As a result of this, the upper body activity happens to be 300% more than what is achieved by using traditional free weights. This feature was actually a part of a scientific study which was undertaken by Dr. Daniel Cipriani, Professor at the department of Exercise Physiology at San Diego State University. And he did find the technology of Dynamic Inertia to be practical and not just a hypothesis. In the following paragraphs, you would come across a description presenting you with the pros and cons of this device, to help you know the product well and take a decision about investing in it. Pros The first advantage of the device is its small size. Most users give the feedback that the device could fit in any kind of luggage. So, those who travel a lot, may find this a smart choice. Speaking about its small size, the female version of the device weighs a mere 2.5 lbs. This makes it an easy equipment to carry anywhere with ease, unlike in the case of dumbbells. The important pros are the device's durability and sturdy built. Wear and tear of products is the biggest disadvantage for any product which is supposed to have a long life. But with this one, your investment is safe as far as the durability is concerned. With this fitness equipment, you need not bother about dying batteries and the need for recharging. As a user, you are responsible for generating the movement. The weight bounces back and forth with the mixed effort of internal resistance and shaft. One more advantage of the device is an instructional DVD which comes along with it. So, as a beginner, you would not have to ponder about how to get started. Furthermore, the equipment comes with a full money-back guarantee, to compensate for the dissatisfaction of the user. The guarantee also includes shipping and return shipping. This leaves you with a worry-free decision of investing on this device. Cons Unfortunately, using this piece of equipment is not much of a help for working out all the muscle fibers in the arm. This is due to its limited range of motions, which is a result of the way it works. Most users have reported that they did not have the feeling of any workout when they used the device with both hands. It is efficient only when worked with one hand at a time. The disadvantage with the instructions in the DVD is that in most of the exercises, the shake weight has been used as a dumbbell. Now with a weight of 2.5 lbs, the device can be attributed as useless if used as a dumbbell. For any kind of exercise, it is important to focus on the positioning of the lower body. This isn't a part of the instructional DVD, where only the upper body posture has been projected. And finally, in contrast to what the makers of the device claim, a mere 6 minutes of exercise with this equipment would not give you lean, sculpted arms and shoulders. Although shake weight may not turn out to be like the way it is advertised, it does have its own share of benefits. For instance, most users have experienced faster healing of their sore arms after using this fitness equipment, and some have also realized that they could type faster. Seemingly, it also does a pretty good job for preventing carpal tunnel syndrome and encouraging better stretching. So, shelling out money on this piece of equipment really depends on your expectations. If you really want to get toned arms in just 6 minutes, then it might not be the right choice for you. Since it comes with a money-back guarantee, you can check it out for yourself.