The design is perfect for use for ass play/teasing, anal training or even punishment, but not well suited for use during "regular" sex. The shape of the probe is smooth and lovely, however, it is designed to be used with a partner, and as such it won't stay put by itself. It doesn't have a bulb shaped base or any sort of ribbing to keep it in place. Because it's somewhat tapered, it will actually come sliding out unless it's kept in place by someone holding onto the handle.