The AP-11 Adapter is designed for Really Right Stuff and Kirk plates that have flash bracket mounting holes (RRS plates have 2 holes, Kirk plates have 1). Adding the AP-11 to RRS or Kirk lens plates allows you to attach Wimberley flash brackets to the top surface of the plate. Your plates must have holes in them to accept RRS or Kirk flash brackets and you must have at least 5/8" clearance between the top of your existing plate and the barrel of your lens.