Strength and Weight
Two key elements of a prized metal bo are its strength and weight. If the bo is made of a heavy material, such as lead or titanium, it will be exceptionally strong but heavy. If a lightweight material, such as tin or copper, is used, the bo becomes capable of bending or breaking. When judging a metal bo on its strength and weight, it is wise to seek balance between them. The staff must be light enough for even the most strenuous workout, but strong enough for striking and able to bear the wielder's weight if necessary.
Flexibility and Balance
Whether made of wood or metal, bo must have some give in the structure or they may crack or shatter when struck. A solid bo should be flexible enough so that you could push down powerfully upon the staff as it is suspended between two bricks without the bo itself bending or breaking. The staff should be balanced so that the mid-point can be held without the bo tipping to one side or the other. While decorative staves may have heads, most practice or practical staves will lack this feature as it unbalances the bo.
Material and Size
There are a large number of different metal alloys and even solid elements, such as lead, offered by bo vendors. Unless your form requires a heavy or unbalanced staff, it is best to stick to the middle of the road for materials. Graphite and aluminum are the most common due to being very sturdy options that are also lightweight and reasonably flexible. What determines the difference between a bo and a quarterstaff is largely its size. While a quarterstaff is commonly as tall as a man's shoulder and as large around as his wrist, a bo should be exactly 1.82m in length and 2 to 3 cm thick.