Don`t be fooled by its size - this bullet is so powerful, it needs to be harnessed! The silver vibrating bullet and attached battery power pack are easy to install. Multi-speed vibrating bullet attaches to harness with velcro. VAC-U-LOCK SPECS: Product Type: Vac-U-Lock Accessory. Features: Compatible with all Vac-U-Lock attachments.Multi-Speed, With Controller Material: Plastic, Velcro. Power: 2 AA Batteries, not included. Color: Silver. Measurements: Long=2.20 inches Wide=1.10 inches.