The Ionic Defibulizer was an invention being worked on by Rick in the the episode Rick Potion #9. Morty refused to assist by handing him a screwdriver, leading to the events of the episode and the Cronenberg-ization of the Prime Dimension.
The almost-completed defibulizer, needing only one screw tightened (before it would explode).
Something about the device was flawed (whether this was on a conceptual level or just a design flaw is uncertain), causing the completed one in the Dimension C-131 to explode, killing both the Rick and Morty of that dimension. The two were supplanted in secret by Rick and Morty of the original dimension.