Surgical clamp. Coloured Scanning Electron Micrograph (SEM) of a clamp used in brain microsurgery. It is just 0.63 millimetres in diameter and is used for grabbing small tumours. The clamp is made of a nickel-titanium alloy and its sheath (yellow) is made of polytetrafluoro- ethene (PTFE) plastic. Springs keep the jaws of the clamp open (as seen here) when it is not in use. The jaws are closed by sliding the plastic sheath over the clamp. Magnification: x17 at 6x6cm size. (See also M390/271 for the clamp with its jaws closed).