Sizing: Measure the diameter of your neck just above your shirt collar
Sizing the REV is fairly simple if you use this handy chart. Remember that fitment is based on personal preference, and sizing isn’t necessarily limited to the measurements shown. If your neck is wider than the inside diameter of the device shown, the device could still fit, and will function properly, but some comfort will be sacrificed. If you are on the edge between a medium and a large but have narrow shoulders, go with the medium.