The stx b+ tree package is a set of c++ template classes implementing a b+ tree key/data container in main memory. designed to be drop-in replacements of the stl containers set, map, multiset and multimap and follow their interfaces very closely. by packing multiple value pairs into each node of the tree the b+ tree reduces heap fragmentation and utilizes cache-line effects better than the standard red-black binary tree. the classes contain extensive assertion and verification mechanisms to ensure the implementation's correctness by testing the tree invariants. to illustrate the b+ tree's structure a wxwidgets demo program is included in the stx-btree-demo package.