According to this link, it's possible the info ye' require might actually reside in the Win32_PhysicalMedia class:
class Win32_PhysicalMedia : CIM_PhysicalMedia
{
string Caption;
string Description;
datetime InstallDate;
string Name;
string Status;
string CreationClassName;
string Manufacturer;
string Model;
string SKU;
string SerialNumber = NULL;
string Tag = NULL;
string Version;
string PartNumber;
string OtherIdentifyingInfo;
boolean PoweredOn;
boolean Removable;
boolean Replaceable;
boolean HotSwappable;
uint64 Capacity;
uint16 MediaType;
string MediaDescription;
boolean WriteProtectOn;
boolean CleanerMedia;
};