The 48 Tools M12 battery holder is a great addition to any Milwaukee user. Simply insert our M12 attachment in any 48 Tools M18 battery holder and you can store both M12 and M18 batteries together. Just bought a new M18 battery No problem!! Simply squeeze the upper tabs on the M12 attachment and remove it to install a new M18 or just to move the M12 attachment to another location on your 48 Tools battery holder. As with all the 48 Tools battery range your battery terminals are protected and the M12 attachment is no exception. With our specially designed cover panel your M12 batteries will be completely protected from harm and any chance of an object damaging the battery terminals. And with the batteries locked in place for use in mobile vehicles they can be mounted in any direction without worry of them falling out or getting damaged.