For the continued and reliable operation of the 3 mass spectrometers in JRC-G.2/METRO nuclear mass spectrometry laboratory, which are 2 TIMS (thermal ionization mass spectrometer) and 1 UF6-GSMS (gas source mass spectrometer) instruments, a full maintenance and service contract, including preventive and corrective maintenance and supply of spare parts, is necessary. If the instruments are not properly and continuously maintained by specialised personnel, the continued full operation of the JRC-G.2/METRO nuclear mass spectrometry laboratory cannot be not guaranteed. Without a full maintenance and service contract, significant delays can be expected for visits of service engineers and delivery of spare parts. As a consequence of the absence of such contract, the successful completion of on-going projects for the JRC work programme is at great risk.