Hi I'm going to use Boost.Pool with UserAllocator mapped directly to Windows API calls ::VirtualAlloc and ::VirtualFree. So it makes no sense to allocate less than SYSTEM_INFO::dwAllocationGranularity, which currently equals to 65536. To my surprise, I have not found anything like this in documentation. But I've seen in source code this: // pre: npartition_size != 0 && nnext_size != 0 explicit pool(const size_type nrequested_size, const size_type nnext_size = 32) So is "nnext_size" what I was looking for ? And what does mean "an extension", is there an official proposal of Pool for future standard ?