These nipple suckers are no joke! A wide opening allows for the suction of a large area. The unique easy-push design creates a powerful vacuum that clings tightly to your skin. As blood flow to the nipples increases, they will become more sensitive. Leave the suckers on or take them off for increased sensitivity during masturbation, foreplay, or sex. Made of premium grade silicone, these suckers are not compatible with silicone lubricants so it is recommended that you use a water-based lube to create a tight seal.