Embodiments of the present disclosure relate to methods, devices and computer readable storage media for determining a transport block size (TBS) for Contention Free Random Access (CFRA) in a random access procedure. In example embodiments, a CFRA request is transmitted by a terminal device to a network device during a random access procedure. The terminal device receives a random access response to the CFRA request from the network device. The random access response indicates a TBS granted by the network device for use in transmission. Based on the granted TBS, the terminal device transmits, to the network device, a first data block with the granted TBS or a second data block to be transmitted and stored in a buffer. In this way, the data loss may be avoided, and the data transmission efficiency may be improved.