Hi-rel power transistors come in multiple packages outlines

LEGACY TECHNOLOGIES Hi Rel Power Transistor line includes a wide variety of T0-254, 257, 258 and 259 packages outlines. Devices are suitable for demanding thermal and electrical management applications of power transistor packages. Available as standard or custom product, firm provides either glass-to-metal seal (GTMS) or ceramic-to-metal sea (CTMS) feed thru technology. A wide variety of enhanced thermal conductivity base materials are available to support demanding power applications.  http://www.legacytechnologies.com