To be frank over 20 years of ski-ing & boarding i've never had fogging problems, & the only folk I do know who have didn't wear them properly...
A-frames air scoop helps considerably keep em clear at all times except when your hat is crunched up & not allowing air to VENT (that's the word take note people)!
You see IF you wear your goggles on your head & not over your eyes then perspiration & hair, clothing etc tend to interfere with the normal operation of these excellent goggles.
Never wear them hanging off your arm, on your neck, sideways on your head etc etc... or you will (as with any goggle) end up with problems).
ALL hair should be pulled clear of the foam area, hats should not obscure the top foam vents.
A balaclava over the face will hinder operation of your goggles, they need air flow as part of the de-misting process.
Air enters the foam "scoops" at the front of the A-frame & exits via the top, it's a smooth & efficient process.
These are "smaller face" goggles & will not fit anyone who needs glasses underneath.
A small aspect of the shape means side view is limited, that said you should always look where you are going (beyond your immediate visible range).
Very flexible moulding makes for a good fit that a few folk find restricts (albeit slightly) nasal breathing on the bridge of your nose, ..i'm one of those people having had my nose torn off (& stitched on) in an accident, but I wouldn't swap these for any other goggles currently (till my vision deteriorates enough to necessitate bigger goggles capable of holding prescription glasses in comfort).
When that happens i'll simply pass them onto my daughter along with the various lenses accumulated.
Mask frame material is soft, squidgey & flexible, making them very forgiving in your kit bag or during a bale.
The flexibility of the mask moulding makes for simple lense exchanges (around 20 seconds) to pop in place whilst on the mountain.
Yes lenses are expensive, but consider them an investment, always try to work your way to 3 varieties in order to deal with the majority of lighting conditions.
Persimmon is typical "general use"
Opt for a pinkish or yellow hue for white out & low level conditions as well as a darker shade (such as VR28) for brighter conditions, this way you effectively have a lense for all seasons & will find your way down most situations with more vision & ability to determine snow lines than the rest of your party, ...which is why mine have lasted so long & are in good condition!
An investment often overlooked by those desperate to hit the slopes,
As We ski & board both Europe & Canada I find the following lenses useful..
Persimmon (standard general purpose lense)
VR50 Pink Iridium / LOW light & flat conditions obscuring snow features.
Medium to bright light. Filters blue light to increase contrast and improve depth perception in a wide variety of conditions.
H.I. Yellow (as above)..High Intensity Yellow
Flat to very low light. Basically a high contrast lens for extremely low light conditions. Features an Iridium coating boosting visible contrast.
VR28 for brighter conditions (smokeier than persimmon)
Good for Medium to bright light. Filters blue light to increase contrast and improve depth perception in a wide variety of conditions.
There is a lot to be said for many of the lenses on offer & whilst costly they pay for themselves when needed (& on mountain shops sell out)...
Mirrored lenses do look flashier, but are costlier & once again 1 mirrored lense is not a guaranteed fix for all conditions).
Basically these goggles offer the following positives...
Anti Fog Treated Lens ..(don't touch inners with fingers ..ever)
Vents & scoops allow entry & exit of air / carrying away internal moisture.
The dual lens (double glazing) designed to reduce fog with a thermal barrier of air.
Polar fleece face foam for excellent moisture wicking abilities & comfort of wear over a long day.
Great impact protection & optical clarity!
..looked after these will last you years offering dependable service.
Like any piece of kit learn how to use it, & work with it to get the best out of it!
Lastly, the goggle bag these come with is good quality & useful to store other lenses you may opt to buy, lenses take up less space than a spare pair of goggles in your pack & make your regular goggles more practical & lightweight when you consider the amount of kit you often need in a mountain environment be it walking, hiking, ski-ing or snowboarding.
Last word, not all straps are helmet compatible, you may require an adjustor to "flare" a head band out around a helmet, check this first before you disregard a good set of goggles based on comfort in & out of a helmet.
expensive but there for the long haul!