rear view mirrors rarely help and often distract. If you can't look behind while riding you just need more practice (unless on a bent). I may just be jealous, i was never allowed to ride with a mirror because a family member died due to a bike rear view mirror, so my dad never let me have one growing up. it was a handle bar mounted one that hit her in the throat. clearly a one in a million, but i think i would find them annoying anyhow.