Plastic collar in new bike's head tube: shipping protection, or functional part?
Hi, my online-purchased bike arrived with a (damaged) plastic collar at the top of the head tube. It's a different color and softer material than the definitely transit-protection-only pieces, and it has a (retaining?) groove or channel around its circumference. Its throat seems just a shade too narrow to accommodate the handlebar stem. Can anyone advise me whether to keep/replace this collar or just discard it? Thanks very much!