Big Bros are a type of Active Protection.
Big Bros are primarily designed to protect large to extremely large cracks. Big Bros are tube like devices that expand by having two unique tubes (one inside of the other). After the trigger is pressed, a spring forces the tubes apart jamming both sides of the Big Bros on opposing sides of the crack. A ring is then screwed down to the desired level prohibiting the tubes to re-contract. Generally speaking, these are not needed on a beginner's rack.