More than half a million so-called “ hoverboards ” are being recalled, according to a Wednesday announcement by the Consumer Product Safety Commission. The government agency noted that there have been 99 reported incidents of batteries that have exploded or caught fire roughly within the last year.

Since March 2016, most self-balancing scooter sales have been halted in the United States anyway after Segway brought a patent suit. Prior to that, the devices were banned by several airlines in December 2015 over the same battery safety concerns.

As Ars reported earlier, the main reason hoverboards have self-destructed is because of their batteries. All of the major hoverboard brands use rechargeable lithium-ion batteries for power, and those can be dangerous for two reasons: cheapness and mistreatment. Li-ion batteries are used in everyday devices such as smartphones and tablets, but typically the companies making those devices can afford to use higher-quality, more expensive batteries.

Affected consumers should check the CPSC list and contact the retailer for a refund, repair, or a replacement.