TM 10-3930-655-24P Code Explanation Items with these codes are not to be requested/ requisitioned individually.  They must be made from bulk material which is identified by the part number in the DESCRIPTION AND USABLE ON CODE (UOC) column and listed in the Bulk Material group of the repair parts list in this RPSTL.  If the item is authorized to you by the 3d position code of the SMR code, but the source code indicates it is made at a higher level, order the item from the higher level of maintenance. Items with these codes are not to be requested/ requisitioned individually.  The parts that make up the assembled item must be requisitioned or fabricated and assembled at the level of maintenance indicated by the source code.  If the 3d position code of the SMR code authorizes you to replace the item, but the source code indicates the item is assembled at a higher level, order the item from the higher level of maintenance. XA - Do not requisition an "XA"-coded item.  Order its next higher assembly. (Also, refer to the NOTE below.) XB - If an "XB" item is not available from salvage, order it using the FSCM and part number given. XC - Installation drawing, diagram, instruction sheet, field service drawing, that is identified by manufacturer’s part number. XD - Item is not stocked.  Order an ’XD"-coded item through normal supply channels using the FSCM and part number given, if no NSN is available. NOTE:  Cannibalization  or  controlled  exchange,  when  authorized,  may  be  used  as  a  source  of  supply  for  items  with  the above source codes, except for those coded ’XA" or those aircraft support items restricted by requirements of AR 700-42. 3