A sex toy includes a mounting ring body (10). The mounting ring body has a center provided with a mounting hole (11) which perforates the mounting ring body. The mounting hole of the mounting ring body has a complex slope shape. The mounting hole of the mounting ring body includes a looped restriction section (111) and an oblique tapered section (112). The mounting ring body has an outer face provided with at least one arcuate groove (12). At least one expanding ring (20) is mounted in the at least one arcuate groove of the mounting ring body.
