With the Size Matters Breast Pump Cylinder, you can increase your breast size and stimulate at the same time Simply attach the cup to any Size Matters hand pump, fit the cup over the breast, and start pumping until you are satisfied. This pump cylinder contains a state of the art air valve that allows for quick and easy disconnection from the pump while maintaining pressure within the cylinder. Use it to enlarge, enhance sensitivity, and stimulate Measurements: 4.65 inches inner diameter, 4.75 inches in depth. Material: ABS plastic. Color: Clear. Note: Requires hand pump, sold separately