Check the listing for details. VEX Robotics Crystal Upgrade Kit A (Part No. 276-2171). Condition: New. Listed at 14.80 USD. The VEX Crystal Upgrade Kits allow you to change the frequency used by the transmitter controlling the VEX autonomous robot. The transmitter included in the Dual Control Starter Bundle uses a standard frequency for all kits. In situations where you want to control two or more robots simultaneously using multiple transmitters, such as during a competition, it is necessary to change the frequency used by the transmitters so that each robot is controlled by a transmitter with it's own unique frequency. Our eBay Store The VEX Crystal Upgrade Kits allow you to change the frequency used by the transmitter controlling the VEX autonomous robot. The transmitter included in the Dual Control Starter Bundle uses a standard frequency for all kits. In situations where you want to control two or more robots simultaneously using multiple transmitters, such as during a competition, it is necessary to change the frequency used by the transmitters so that each robot is controlled by a transmitter with it's own unique frequency. Product Features Allows for Simultaneous Operation of Multiple Robots A Must Have for Competitions Crystal Upgrade Kit-A Includes Four (4) New Channels and One (1) Insert Guide New Channels: 65, 69, 81, 85 Requires VEX Robotics Design starter kit