Sometimes, a match is considered as a series of smaller matches, which may take place concurrently, consecutively, or even in different shows. The most common form of a series match is extending the one-fall concept to a series of falls, the most common being the best two out of three (known as a two out of three falls match). These types of series matches are often booked to the final match to emphasize the equality of the wrestlers involved, however, longer series may be shortened due to storyline or other factors. Series matches may involve the same match throughout, or may use different matches for some or all of the series. A series match may or may not involve the same wrestlers throughout (such as when a main competitor is forced to use a substitute in the event of an injury partway through).