The Tanksert disc is a composite type, with flat seat sealing configuration. It is composed of an outlet ring for positive dimensional burst control and protection of the top section – a slotted metal top section which is the controlling burst member – plastic seal which isolates top from the tank media and prevents leakage - vacuum support which prevents seal from becoming damaged, should a pre ssure surge occur during transit or unloading. The vacuum support is also specially designed with an off-set section to assist in positive alignment during installation. These discs are exceptionally accurate and fit standard threaded or bolted railroad tank car safety vents.