(21)While the clearing thresholds should be set taking into account the systemic relevance of the related risks, it is important to consider that the OTC derivatives that reduce risks are excluded from the computation of the clearing thresholds and that the clearing thresholds allow an exception to the principle of the clearing obligation for those OTC derivative contracts which may be considered as not concluded for hedging purposes. More specifically, the value of the clearing thresholds should be reviewed periodically and should be determined by class of OTC derivative contracts. The classes of OTC derivatives determined for the purpose of the clearing thresholds may be different from the classes of OTC derivatives for the purpose of the clearing obligation. In setting the value of the clearing thresholds, due consideration should be given to the need to define a single indicator reflecting the systemic relevance of the sum of net positions and exposures per counterparty and per asset class of OTC derivatives. Furthermore, the clearing thresholds being used by non-financial counterparties should be simple to implement.