A type of 40mm grenade, the mei hellhound is used with several types of grenade launchers, such as the m79, the a203, or milkor mk-1. It’s primary feature is a fragmentation sleeve on the outside of the grenade, plus extra explosives. These cause the mei hellhound to be far more lethal than ordinary 40mm grenades.
Getting hit in the face with a Mei Hellhound shot from a M79 will not improve your day. Ever.