SheFly,
Mine is a medical alert-it needs to be seen in case of an emergency. To answer your question, the one I bought to go out in is an 8inch (which is huge but my choice was 7 or 8) but I did that on purpose. It can be adjusted down to wear against my bare skin or up to wear over my jerseys. When it is cooler I wear it over my jersey and it is bright-because if something happens I want to make it easy for emergency personnel to see it.