Spring toggle anchor (butterfly hollow wall anchor) is designed for hollow substrates such as plasterboard, hollow block and plywood. It includes threaded bolt and spring-operated butterfly wings. Wings are folded to pass through pre-drilled hole and spring open behind the panel to create firm back support. Widely used for mounting light & medium loads like lamps, shelves and decorations on hollow walls. Sizes M3~M6. Zinc plated finish available.