McCallum's drone extenders fit in your drone top to lengthen the drone and lower the pitch. When they're paired with your B Flat pipe chanter, you'll be set up to play your pipes in B Flat, or at 466 Hz. With the extenders in, you may need to move the bridle ever so slightly to open the tongue. The extenders fit McCallum, MacRae, and Naill drones. Set of 3 Drone Extenders.