Provided are a method for a first device carrying out wireless communication, and a device supporting same. The method may comprise the steps of: receiving, from a base station, information on the number of sidelink synchronization signal blocks (S-SSBs) transmitted in an S-SSB period; and, on the basis of the information on the number of S-SSBs, transmitting, in the S-SSB period, one or more S-SSB including a sidelink primary synchronization signal (S-PSS), a sidelink secondary synchronization signal (S-SSS) and a physical sidelink broadcast channel (PSBCH). Here, the number of S-SSBs may be selected from among one or more element included in a set of the number of S-SSBs transmittable in the S-SSB period, wherein the set of the number of S-SSBs transmittable in the S-SSB period may be configured differently on the basis of sub-carrier spacing (SCS) and frequency range (FR).