In addition to the branch and club structure, Special Interest Groups (SIG) exist which focus on a specific area or type of model building, for instance a particular aircraft such as the Tornado, a time period like the Cold War, a manufacturer such as Airfix or a genre like science fiction and fantasy. SIGs often transcend club and branch boundaries, being made up of modellers from around the world sharing a common interest. As a result, most SIGs do not meet up on a regular basis like clubs, but instead communicate more frequently online.