(18)In order to ensure the objective and effective application of the definition of systematic internalisers in the Union in accordance with Article 4(1)(20) of Directive 2014/65/EU, further specifications should be provided on the applicable pre-set limits for the purposes of what constitutes frequent systematic and substantial over the counter (OTC) trading. Pre-set limits should be set at an appropriate level to ensure that OTC trading of such a size that it had a material effect on price formation is within scope while at the same time excluding OTC trading of such a small size that it would be disproportionate to require the obligation to comply with the requirements applicable to systematic internalisers.