We have rarely heard of a SRAM Eagle AXS battery being damaged or lost on the trail, but given it' position on the rear derailleur, some protection makes real sense. For the release of Eagle GX AXS, SRAM created an ABS plastic cowling with ventilation that has been designed to protect the battery while installed on the derailleur. This AXS battery cover fits all AXS mountain bike derailleurs, and it is sold as this standalone item.