Mail-list failed to send me the reply from Ion, attempting a reply anyways... *(mail-list owner, what i do wrong?)* Thanx Ion. I got it to work as you suggested. Found old gtest - loggs that confirmed that the cache_last option wasn't needed in old code so this must be a change . Oh, and yes. uint64_t... :-) .. yes I modified the code after cut-paste. The docs for 1.55 intrusive slist under "Using base hooks http://www.boost.org/doc/libs/1_55_0/doc/html/intrusive/usage.html#intrusive..." shows example with push_back() without mentioning cache_last. Mabey it should be push_front() in that example? Nifty to get to pick and choose level of overhead :-) /Jonas