Cardas Binding Posts are sold in pairs and come with a dual mounting plate. The SBPI allows Cardas Binding Posts to be mounted individually. Cardas Single Binding Post Insulators are used in place of the dual mounting plate that comes with most Cardas Binding Post sets. When your binding posts are not on the standard 3/4″ centers that the dual mounting plate provides, this is what you need to mount your Cardas Binding Posts. The SBPI insulators are sold in a set of two, one red and 1 black.