Pelvic Toning Devices fall into a number of different types:
barbells, vaginal weights or cones designed to be held in the vagina. The action of passively/actively retaining the device internally is supposed to improve muscle tone. Barbells are made of smooth, polished solid stainless steel, cylindrical in shape, with a rounded ***** at each end. They typically weigh one pound (454g) and measure approximately 6¾ inches (17.1 cm) in length with a diameter of one inch (2.5 cm) at the widest part. Being made of stainless steel, vaginal barbells are nonporous and can be wiped clean with a cloth moistened with mild soap and water.
electro-stimulation or TENS devices that administer an electrical current through an internal probe. The current stimulates the adjacent muscles to twitch.
rubber resistance balls and indicators. These devices provide a nominal resistance to squeeze against. An advantage of rubber bulb devices is that they provide visual feedback (via a gauge) of how much pressure is being applied.
progressive resistance vaginal exercisers with springs are the only devices that meet all of Kegel's criteria. They provide a biofeedback that the correct muscles are being engaged and are capable of fulfilling the basic fundamentals of an exercise regime by applying a variable and increasing resistive force to maximise the exercise effort.