typedef struct _MM_SUBSECTION_AVL_TABLE
{
     MMSUBSECTION_NODE BalancedRoot;
     ULONG DepthOfTree: 5;
     ULONG Unused: 3;
     ULONG NumberGenericTableElements: 24;
     PVOID NodeHint;
} MM_SUBSECTION_AVL_TABLE, *PMM_SUBSECTION_AVL_TABLE;

Windows Vista Kernel Structures