bras is the recommended extension for files generated by BinarySpikeMonitor. The can be decoded to the human readable ras format using the provided tool Auryn Binary Extract (tools/aube) which is compiled by default (versions >0.6.1). Binary spike raster files provide a significant speed advantage over regular ras files because the output does not need to be formatted. Formatting is done offline by aube or custom written analysis software. Also from an analysis point of view binary raster files are advantageous because they allow quick access to any time point (and time range) within the file whereas ASCII based ras files needed to be processed sequentially from the beginning. Finally, binary spike raster files are smaller in size and can be compressed more efficiently than ras files.