A large sealed ampoule of pressurized supercritical Xenon gas.  Length is about 12cm and diameter is about 7mm.  Purity is 99%+.  This amazing sample will phase change before your eyes when cooled below 16°C.  Let it warm up above 16°C and watch it boil away into the gas phase again.  The last photo shows it cooled down in the liquid phase.  This is truly an amazing sample and fun to watch!