CB Range discussion

Should I go with Steel/Chrome or plastic for better comfort and hygiene? I plan to wear it full-time, leaving it on for weeks or even months at a time. My trusted friend will hold the keys for me. My main goal is to really lower my sex drive and curb masturbation. This is my first CB purchase; are there any other things I should keep in mind while shopping around? There are so many models out there, but their sizing numbers confuse me.