Nipple suction increases sensitivity and temporarily engorges as it draws increased circulation into the area. You can even detach the cylinders and keep them on while you fool around. Just place the industrial-grade acrylic cylinders over your nipples, using lube if necessary to make it airtight. Pump the hand bulb to initiate suction. When done, a quick release valve allows you to immediately release the pressure, effectively freeing your nipples. Cylinders measure 2.75 inches inner length, with an inner diameter of 0.6 inch. Connector tubes are each 9.5 inches long.