The cobra roll is a double-inversion which resembles the head of a cobra. Riders travel up through a half-loop, corkscrew perpendicular to the first direction, enter another corkscrew that merges into a downward half-vertical loop that exits in the parallel but opposite direction of the entrance.
The first roller coaster to use a cobra roll was Vekoma's Boomerang model, the first of which to open was Boomerang at Bellewaerde, in 1984. Now, over 150 roller coasters include a cobra roll. The element is widely used by Bolliger & Mabillard roller coasters.
There is some confusion about the naming of this element, different manufacturers give different names to their inversions. Cobra roll is the widely accepted name, and the name used by Intamin and B&M, however it is sometimes known as a Boomerang, due to the popularity of the Boomerang by Vekoma.