Thermos bottles are smaller vacuum flasks fitted in a protective casing. The main usage is to support or hold the flasks and beakers during experiments. The final two attributes of Erlenmeyer flasks make them especially appropriate for recrystallization. The artifacts included necklaces, plates, gold earrings, finger and toe rings, bowls and flasks. Athletes were provided with refillable steel flasks. By 1880, Navajo silversmiths were creating handmade jewelry including bracelets, tobacco flasks, necklaces and bracers. Solvent pots are not usually bombs, or even Schlenk flasks in the classic sense. Vacuum flasks, or Dewars, are silvered to approach this ideal. Pasteur also used swan neck flasks containing a fermentable liquid. The neck of volumetric flasks is elongated and narrow with an etched ring graduation marking. Stirring bars or other stirring devices suited for round-bottom flasks are sometimes used. However, there are other vacuum flasks. Two more retorts were added in 1904 and production amounted to 200 flasks per month. The cargo included approximately of metallic mercury in 1,857 steel flasks stored in her keel. Iron is an exception, and iron flasks have traditionally been used to trade mercury.