Best for under a helmet
592337
Just what the doctor ordered to keep my noodle warm
1292549
Summers are hot and humid where I live, especially this summer with early morning temps in the low 90s and daytime at 100. After an hour or so cycling, the terry pads in my helmet were soaked and sweat dripped for the rest of my ride. The Headsweats cap is perfect for absorbing sweat and wicking it away. I can easily throw this cap in the washer along with my cycling kit. I don't see many cyclist in my area wearing caps under their helmet, but I wear it every time I ride.
2435074
TL;DR - Don't buy these for wearing under a motorcycle helmet.  Otherwise, they work really well.

The ear plugs seem to work really really well.  Be careful as it seems easy to stick them in too far.  Don't bother if you ride a motorcycle.  The ear plug itself is a post with a tip, and it sticks out too far to comfortably get a full face helmet over it.  Taking the helmet off was pretty painful, actually, because I couldn't get it off without getting caught on the plug and ripping them out of my ears.
4698515
This balaclava is ok.  It fits well under a motorcycle helmet and keeps the head well insulated.  Its greatest strength is the long neck.  Put it on before putting on your jacket, no wind gets in or around your neck.  The one thing I don't like is how it fits around the nose.  Because the opening is not cut for a nose and there is no easy ventilation for the mouth, warm breath in the cold air shoots right up the sides of the nose to my glasses fogging them up quickly when not moving.  I have quite a few balaclavas and this one rates about midway.
3296069
Does a great job channeling the sweat from my eyes. Very comfortable and thin so it fits well under my helmet.
1189418
I purchased this to wear under my full face motorcycle helmet and for those blizzard like days on the slopes.  It works really well for both.  I was afraid it might be too thick for my helmet but it fits like a glove. The material is thick enough to provide protection but thin enough to not interfere with my other equipment.

- I do suggest that you wash it before you wear it.  You never know what sort of chemicals and other paraphernalia have come in contact with this. I hand washed this with mild soap and the water in the sink turned blue. Just a suggestion.
3962750
I bought these to wear with my Bell Rogue helmet and love it. The dual pane does not fog over with the hot air from my breath coming up from the muzzle. I have to use the strap to keep the glasses pulled tight around my face and block the cold air, but it's narrow enough to not cause problems with the fit or comfort of the helmet. I will be ordering some clear ones next.
2656197
Highly recommended.  I have a 26" head, (med helmet size) and it fits good, not tight.  If you have  a large head this will work for you too.  Caution if you have a small head.

 I used to loose visibility on my rides as streams of water rolled down my sunglasses...No more!  I can see freely now!  This thing rocks, I am using it under my hockey helmet, and my motor cycle helmet too.  It fits nicely and does it's job.  Doesn't' seem to hold in more heat that without it...but on cold days, I can feel a difference, probably because I can cover the tops of my ears with it.
444057
I like it...I wore it under my helmet. Works fine looks awesome.  Not stretchy material.
4929
I don't ski, or snowboard, or skate.  But I do ride a bike in the winter, for my commutes to work.  Up until I received this Traverse helmet, I had been wearing a bike helmet over a stocking cap.  It was the only way I could keep my head warm when the temperature dropped below 50 degrees.

This helmet from Traverse is a much better solution for me.  Though the ear flaps are removable, I always keep them on.  The flaps do a very good job of keeping my ears warm.  The insulation in the rest of the helmet successfully keeps the rest of my head warm too.

All in all, the helmet is warm and comfortable, and has become my go-to protection on cold days.

One minor complaint though: when I'm moving a bit faster on my bike (say, 20 miles per hour), I notice a howling sound, due to the way the vents on the helmet catch the air flow.  It's not a horrible sound (it kind of reminds me of sitting indoors and listening to the howl of wind caused by a poorly insulated window).  But the sound is noticeable.  And, with the ear flaps further reducing my ability to hear, I sometimes worry that I may not hear when a car is coming.  I can deal with the noise, because I really like the warmth...I just need to keep a closer eye on my surroundings.

I'm happy with the helmet: I finally have a way to keep my head warm in the winter.
4209668
I wear this on construction sites under a hard hat. It blocks the wind very well and keeps me warm as well. Considering the material is rather lightweight I'm very happy with the performance. I tried a Turtle Fur and Carhartt balaclavas and found them both fitting small and having large gaps of exposed skin either on the neck and sides of the eyes. I don't have an exposure with this balaclava. The only down sides are after 5-6 hours my ears get sore from the pressure on them. Also, if you wear glasses, safety glasses or goggles they will fog up if you have your mouth covered. Not sure how to avoid this, it's probably just something one has to deal with.
2538365
Very good quality helmet! I actually bought this to go caving, but haven't done so yet. :) It should provide more than adequate protection for most sports, but I wouldn't recommend it for motorcycle riding on the highway. :)
722913
Excellent headband under my cycling helmet. Very happy with purchase. I can pull it down enough to cover my ears to block the wind too.
4190910
The Good:
Fits well enough under a helmet, and not having a gap for cold air to get between your neck gaiter and helmet liner is a good thing. Stops the wind.

The Bad:
Cannot be pulled up over the nose, as little air gets through the fleece material. Just fogs up your goggles\glasses. The fleece is poor quality, and for guys, if you did not shave ten seconds before wearing, your whiskers will pull the material apart, so you'll have black fuzz all over your face, and it's actually pretty hard to get off. Because the fleece is so impermeable, your breath condenses on the inside of the fabric and makes it a runny, slimy mess.

The Solution:
Use this in conjunction with a proper skiing face protector and keep the Shellaclava below your chin. You won't have the slimy fuzzy mess and your neck will not experience cold drafts, plus your goggles won't fog over.
205556
Very comfortable, light weight helmet which does not give you the mushroom head look. There is not to much foam/padding, so I plan to use it during the summer. I have a HJC-IS Cruiser half helmet with a lot of foam/padding which is very comfortable but can get hot.
3733419
Best fitting and most comfortable helmet I've had. My only complaint is the strap loosens every time I unbuckle the helmet and then I have to tighten it the next time I put it on. - Need a better way of securing the strap so it doesn't slip.
4455958
Wear it under the helmet at the park on hot days, or long distance pushing or downhill on a longboard, really works well under both a regular helmet and a Bell Drop full face, if it's hot and I'm wearing a helmet I use this.