A container with the inner perimeter maintained at constant temperature ±0.1 °C ( isoperibol ) or at the same temperature ±0.1 °C as the calorimeter vessel ( adiabatic ) during the test. To minimize convection, the sides, top, and bottom of the calorimeter vessel shall not be more than 10 mm from the inner surface of the jacket. Mechanical supports for the calorimeter vessel shall be of low thermal conductivity.