Defender & Defender Lite are one size fits most Adult protectors. It is built to be compatible with Small, Medium, and Large adult braces. If one of these braces fits you, this protector will likely fit as well.
Defender Jr is a one size fits most youth protector. It is built to be compatible with Tyke or Prodigy braces. If one of these braces fits you, this protector will likely fit as well. While this protector is adjustable in the shoulder, it may not be suitable for children on the lower end of the Tyke size