Third Eye Helmet MirrorThird Eye Helmet Mirror. This mirror clamps to the lip of Hard Shell helmets. The maximum opening of the clamp is approximately 1/2 inch. The original helmets all had a ridged outer shell and this mirror was designed to clamp to that outer shell. The clamp can also attach to the visors of many helmets. The glass mirror is 1 1/2 inches in diameter & it is laminated into the mirror shell making it shatterproof730366030006