TheRevolabs HD 4 Slot Chargercomes with 4 HD Battery Charger Adapters. It allows users to easily replace batteries in the field.Users can open the back of the microphone, take out the previous battery, and replace it with a new one. Also,with the battery charger adapter, users can charge spare batteries usedfor theHD Wireless Microphone Systems. This allows users to have charged batteries on hand for use.