The roughhead or onion-eye grenadier Macrourus berglax can reach up to 1 m in length. It has a large, broad head about 25% of the body length. The snout is prominent and pointed. The mouth is small and located on the underside of the head. A short chin barbel is present. Its relatively short trunk tapers evenly to a pointed tail. It has a tall truncate first dorsal fin, and small, continuous second dorsal and anal fins. The roughhead grenadier is ash grey in colour with a darker chest. The first dorsal and pectoral fins are dark sooty grey.