typedef enum _PP_NPAGED_LOOKASIDE_NUMBER
{
         LookasideSmallIrpList = 0,
         LookasideLargeIrpList = 1,
         LookasideMdlList = 2,
         LookasideCreateInfoList = 3,
         LookasideNameBufferList = 4,
         LookasideTwilightList = 5,
         LookasideCompletionList = 6,
         LookasideScratchBufferList = 7,
         LookasideMaximumList = 8
} PP_NPAGED_LOOKASIDE_NUMBER;

Windows Vista Kernel Structures