The special interest groups (SIGs) are user groups that requires payments. The module has been released recently. If you’re using membership module, you can integrate it into your membership application and give members the options to join the special interest groups when they are applying memberships. It allows you to have the separate membership payment for regular membership and for special interest groups in one payment transaction.
Integrating SIG to membership is easy; it takes two steps: 1) Add special interest groups in the SIG module. 2) Add the SIG section to your membership application. For detailed information, visit the help file Special Interest Group with Membership.