The safety selector on the AR-15 is a simple lever. When parallel to the barrel, the safety is engaged, when perpendicular to the barrel the safety is disengaged (in a SAFE/FIRE configuration).
For those who prefer a high grip, actuating the safety requires a bit of a reach to engage the safety. Flipping the safety to the "FIRE" position is easy; going from "FIRE" back to "SAFE," on the other hand, requires a bit of dexterity.
Blackhawk's AR-15 Offset Ambidextrous Safety Selector addresses this by introducing a 45-degree offset from MilSpec safety selectors, with more of a reach required to disengage the safety but less required to engage. It's a small change, but can make a difference particularly for those with shorter fingers.
It takes a little getting used to, especially if you're used to the conventional safety lever, but with a modicum of practice it quickly becomes second nature. Available as a standard right-hand safety or (as shown) ambidextrous.