A Whisker Biscuit allows you to keep an arrow balanced between the bow and bowstring. Its almost-circular interior brush looks like the bristles of a beard and support the arrow. They allow the arrow's fletching, whether feathers or vanes, to pass without interference, as well. Your choice of Whisker Biscuit depends on your arrow's size.
Sizing Your Biscuit
As you choose your Whisker Biscuit, remember: you can fit a smaller arrow in a larger arrow rest better than you can fit a large arrow in a rest that's too small. According to the manufacturer, the Whisker Biscuit comes in three sizes. The smallest a 0.30-inch inside diameter. It's suitable for A/C/C carbon arrows, Outserts, carbon or Axis arrows, as well as 17XX or smaller aluminum-shaft arrows. A medium Whisker Biscuit has an inside diameter of 0.320 inches and can handle internal-component carbon arrows and 19XX or smaller aluminum shafts. The large Whisker Biscuit's 0.395-inch, inside-diameter opening accepts 23XX or smaller aluminum arrows. Finally, the Whisker Biscuit for bow fishing has an inside diameter of 0.360 and accepts unfletched fishing arrows