Boost the pleasure of your TENGA Onacup with this vacuum controller, which adds sensual sensations to your masturbation session plus penis-swelling suction to grow your erection size. Set includes a vacuum controller, adaptors and a Deep Throat Onacup. Simply slide the electronic lid over the top of your Onacup, over the airhole, then press the black button to switch on the vacuum. As the air is gently extracted the pressure within the Onacup increases, creating a suction that gently grows the size of your manhood. As the pressure builds, every movement within the spongy internal sleeve feels deliciously exaggerated, for pleasure that slowly intensifies, while building your erection size as you use it. Simple 1 button operation means you stay in control at all times. Please note: Get the best from your TENGA controller by only using it with alkaline batteries.