Sunglasses are one of the most important part in your snow ski equipment.
They are
protecting your eyes and improving snow ski vision. They are normally tinted in order to reduce sun glare, which happens to twice as during winter since snow reflects light. They also
protecting you from the UV rays,which can make
seriously damage to your eyes and skin.You can't ski without ski glasses
Kinds of sunglases
Sunglasses come in three kinds: glacier sunglasses, skiing and snowboarding, and polarized.
Glacier sunglasses filter as much as 90% of sunlight and are ideal for activities involving prolonged sunlight exposure like glacier walking and cross-country skiing, normally with side covers to shield from UV rays and also prevent the wind from getting into the eyes.
They are not good for fast ski runs.
Skiing and snowboarding sunglasses, on the other hand, are great for
activities that involve rough and fast movements, such as ski racing and snowboarding, made up of l
enses that protect from bumps and impact and they must be
very durable with the headband attachment,so they cannot fall off.

Polarized sunglasses are fitted with specialized lenses that reduces glare while at the same time maintaining clear vision, typically used in the mid-afternoon or extremely bright days where sunlight is at its strongest.
Buying tips
When you're buying sunglasses for skiing, here are a few things to take note of:
UV protection: Make sure that your sunglasses provide at least 95% protection from UVA and UVB rays, most especially if you'll be spending a lot of time outdoors. Long-term UV exposure can lead to very serious and permanent eye damage.
Lenses: Choose lenses made of polycarbonate because they are shatter-proof and offer wide UV protection. They might be more expensive but will outperform cheaper lenses, which translates to a good investment in the long-run. Additionally, rose or yellow-orange tints enhance contrast and provide effective glare reduction.
Durability: Choose sunglasses made particularly for winter use. Summer sunglasses tend to fog up and sometimes can even crack from the old, giving you insufficient protection.
Peripheral vision: Look for wide, wraparound lenses offering 180-degree views of the slope. Wind and sun shields should protect the eyes but must still maintain full vision.

I use Scott sunglasses ,and i can tell you that they are excellent.They fit very good,and they are for all weather conditions because i can switching lenses.You can see that this sunglasses are professional skier's choice.
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