Since the beginning of time, pull-ups and chin-ups have been improving physiques. Today, many fitness enthusiasts such as Crossfitters, P-90X'ers, bodybuilders and home fitness buffs still view the chin-up or pull-up as a staple upper body movement for strength, tone, and muscle endurance. It's no wonder the military has had the chin-up/pull-up as a core movement for decades.
With the at home fitness trend blossoming, the demand for portable, home chin-up bars has been booming. The market is made up of cheap single chin-up bar's that can be screwed into the door frame to multi-grip chin-up bars which can also be used for dips, sit-ups, and push-ups. Quality runs the full spectrum, but I recommend not skimping on something that has to support your weight. In fact, if you weigh over 300 lbs you will need to stick to the commercial grade equipment.
The bars are typically made of a heavy steel, but there are differences in brands. If you are over 200 lbs., I suggest you read a number of reviews before investing your hard earned money. It is not the intent of pull-ups or chin-ups for the bar to bend as you move up and down.
You will spend between for a cheap unit to for the branded, popular P-90X Beach Body unit which has many more benefits. There are also non-branded bars that have just as many benefits, at a much lower price point.
Some of the things to look out for when purchasing include: the width of your door and the thickness of the door. Some older homes, especially in New England might not work with many of the bars on the market. I would not recommend using the tools provided with your purchase, but utilize a good power drill as many bars have 6-8 screws that need to be firmly fastened. If your door is in excess of 32" wide, you will need to research the manufacturers carefully as some will not work beyond that width.
Many of the chin-up bars have inferior foam that will rip away after limited use, so you will need to be aware of this defect before you purchase.
If you are not handy, some manufacturers seem to have rushed their instructions and it can become a nightmare to get the bar put together just right. Read the reviews to determine who to look-out for if this describes your handy skills.