A mirror tournament (verb "mirroring") is a tournament where the host obtains the question set from a different tournament, such as a housewrite or a vendor, rather than writing the questions itself. For example, the 2013 Yale BHSAT tournament had a main site at Yale, which is *not* a mirror site, but other tournaments outside Yale which agreed to use the set, such as ATROPHY at Northern Illinois University, are "mirrors" of the original set. In the strictest definition of a mirror, the host team does no editing or writing (and, if it's a college event, participating teams do not submit packets); in its looser, more common definition, participating or host teams are often required to submit packets regardless of whether they attend the main site or a mirror. Recently, the term "mirror" has expanded even more broadly to merely mean "site where a question set is used," including the main site.
When sets are mirrored internationally in Canada and the UK, there may be country-specific modifications to the set.
The nationwide regional tournaments ACF Fall, ACF Regionals, and NAQT Sectionals (And formerly TRASH Regionals) are not traditionally considered mirror tournaments, since the editing comes from a single centralized source not directly affiliated with any particular regional tournament. However, schools that host these tournaments are often known as mirror sites.
For tournament mirrors, the question writers usually charge $10-$20 for each team participating in a high school set mirror, and $30-$40 for each team participating in a collegiate set mirror. About 25% of a mirror's revenue is paid back to the original producers of the set.