An apparatus of a User Equipment, UE,, operable to support variable size buffer status reports, BSR, format comprising: one or more processors being configured to: identify one or more of a plurality of priority classes to be reported and a corresponding buffer size for each of the one or more of the priority classes; and encode a priority class bitmap field comprising a plurality N of contiguous bits, wherein each bit of the priority class bitmap field corresponding to a respective one of the plurality N of priority classes, and the buffer sizes for the one or more of the plurality of priority classes in one or more corresponding buffer size fields, of a BSR for transmission to a Base Station, BS,, wherein each bit of the priority class bitmap field set to a first state indicates that the buffer size field for the corresponding one of the one or more of the plurality of priority classes is included in the BSR, and wherein each bit of the priority class bitmap field set to a second state indicates that the buffer size field for the corresponding one of the one or more of the plurality of priority classes is not included in the BSR; and a memory interface configured to send to a memory the BSR. one or more processors being configured to: identify one or more of a plurality of priority classes to be reported and a corresponding buffer size for each of the one or more of the priority classes; and encode a priority class bitmap field comprising a plurality N of contiguous bits, wherein each bit of the priority class bitmap field corresponding to a respective one of the plurality N of priority classes, and the buffer sizes for the one or more of the plurality of priority classes in one or more corresponding buffer size fields, of a BSR for transmission to a Base Station, BS,, wherein each bit of the priority class bitmap field set to a first state indicates that the buffer size field for the corresponding one of the one or more of the plurality of priority classes is included in the BSR, and wherein each bit of the priority class bitmap field set to a second state indicates that the buffer size field for the corresponding one of the one or more of the plurality of priority classes is not included in the BSR; and identify one or more of a plurality of priority classes to be reported and a corresponding buffer size for each of the one or more of the priority classes; and encode a priority class bitmap field comprising a plurality N of contiguous bits, wherein each bit of the priority class bitmap field corresponding to a respective one of the plurality N of priority classes, and the buffer sizes for the one or more of the plurality of priority classes in one or more corresponding buffer size fields, of a BSR for transmission to a Base Station, BS,, wherein each bit of the priority class bitmap field set to a first state indicates that the buffer size field for the corresponding one of the one or more of the plurality of priority classes is included in the BSR, and wherein each bit of the priority class bitmap field set to a second state indicates that the buffer size field for the corresponding one of the one or more of the plurality of priority classes is not included in the BSR; and a memory interface configured to send to a memory the BSR.