The unique shape of bullets/egg vibrators make them very versatile. They typically measure only 1 inch by 3 inches, and they’re attached by a small cord to a control unit/battery pack. Made of hard plastic, you can use them externally, insert them into the vagina or into the anus (best to use a condom when using them anally). They allow for more than 1 intensity level and some offer varying types of vibration (pulsating, surging, escalating, and roller coaster). Some bullet vibrators even come with sleeves that give a more sensual feel.
