The SX20 is the latest in the SX range of stopped-flow reaction analysers from Applied Photophysics and is used to study transient and pre-steady-state kinetics of fast, liquid-phase reactions. The SX range has, since its introduction over 15 years ago, established itself as the first choice of those involved in stopped-flow kinetic research. The SX20 and its predecessors offer unrivalled performance, as well as a host of upgrade opportunities for the detailed investigation of chemical and biochemical reaction mechanisms