A very simple and inexpensive electrolytic jet thinning apparatus for rapid thinning of metal foils for transmission electron microscopy has been described. Regarding the specimen holder assembly, either a polytetrafluoroethylene (PTFE) holder or a platinum tipped locking tweezer‐type holder, can be attached electrically and mechanically to a micromanipulator to be used in the same jet thinning apparatus. This gives a unique feature to our unit, in which the specimen remains above the electrolyte during the polishing process. Also the constructional simplicity of the unit provides easy drainage of the electrolyte for lengthy polishing and a simple way of stopping the thinning process. Transmission electron micrographs of bombarded and unbombarded specimens electrothinned in the unit are presented herein.