A second RAN node (2) associated with a second RAT sends a radio resource configuration of the second RAT to a radio terminal (3) via a first RAN node (1) associated with a first RAT. The radio resource configuration explicitly or implicitly indicates at least one numerology that is included in multiple numerologies supported by the second RAT and is different from a reference numerology. It is thus, for example, possible to allow a radio terminal to be configured with a numerology of a cell served by a secondary gNB or a target gNB in Inter-RAT Dual Connectivity between E-UTRA and NR and in a handover from E-UTRA to NR.