For replacement visors and care products, see luxury motorcycle helmets.
Most manufacturers recommend replacing a motorcycle helmet every five to seven years even without a crash, since the internal materials that absorb impact degrade slowly with heat, sweat and UV exposure. The shell can look fine while the protective layer underneath has already lost some of its effectiveness.
A certified helmet carries a label inside the shell showing the standard it meets, along with a homologation number that identifies the specific model tested. This label is worth checking on any helmet, since it confirms the exact helmet in your hands passed the test, not just the range it belongs to.
To compare our full face and open face ranges side by side, see custom motorcycle helmets.
Getting helmet sizing right starts with a proper head measurement, taken with a soft tape around the largest part of the head, just above the eyebrows and ears. That figure points to a starting size, http://globaldream.or.kr/bbs/board.php?bo_table=sub08_02&wr_id=440840 but it is only a starting point, since head shape varies as much as head size.
Visors are a wear item, not a lifetime part of the helmet, and most riders find a spare on hand is worth having, especially before a long trip.