Great for under helmet!
927860
Works great at helping to keep the sweat out of my son's eyes under his football helmet!  Glad we tried it!
10395
Use these under my helmet for mountain biking.  So much easier to focus on the task at hand without sweat dripping.  Not a drop escapes.
3990461
This fits perfectly on my ballistic FAST helmet in Large. Its not too tight either, but I do have my doubts about this fitting on an XL shell. So, long story short, L and below? Perfect!
3008266
(Used under a full face helmet - motorcycle )So I like this, it fits great, doesn't slide over my eyes when I put my helmet on, tucks in nicely and I can tighten my chin strap without issue.

I'm only saddened in that it breathes quite a bit. I get a c onsiderable amount of flow that causes cold turbulence near my mouth. But I'm getting closer to what I want and with the weather getting warmer I think I'll stick with it this season.

The fact that it doesn't slide down when I put my motorcycle helmet is my favorite.

It seems a little thick on the top end but that might be necessary. But I may just like my helmets a little on the tight side.
3649754
I bought this to wear under my cycling helmet and it is working out perfectly. The product is well made and I would recommend it to anyone!
1817169
I bought this to wear under my Stormtrooper helmet.  It's great!  It wicks away the sweat and keeps me comfy.
1228782
Works well as a liner under my motorcycle helmet.
1572060
This has helped a lot since motorcycle helmet clamps underneath the rear seat aren't a thing anymore. I always leave it on the bike for ease, and it doesn't really drag from the look at all (at least not on a naked bike). I've carried a gallon of milk, helmets, and take out food all with no problem.

<a data-hook="product-link-linked" class="a-link-normal" href="/PowerTye-50152-Black-15-34-X15-34-Cargo-Net-featuring-6-Adjustable-Hooks-Tight-2-34-x2-34-Mesh/dp/B0022ZXO40/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">PowerTye 50152 Black 15"X15" Cargo Net featuring 6 Adjustable Hooks & Tight 2"x2" Mesh</a>
2528590
I was looking for something to wear under a half shell motorcycle helmet that protected my face in the wind as well as stopping the wind from penetrating through the material onto the facing skin. This codegear hood does a very good job. The hood can be used as a neck gaiter, head cap, full face mask with slit for the eyes. I don't feel the wind penetrate onto the facing skin. The lite hood fits snuggly but not too tight under the helmet. Well worth the money :)
1010971
This BikeAnything thermal helmet liner came in at the perfect time, temperature has started dropping here in California (yea I know we have it good) and I was looking for a liner to go under my helmet to help with the colder temperature. This liner is made out of 15% spandex so it's pretty elastic and hugs your head nicely, the liner was a tad too long for me and it covered my eyes. I had to pull the liner towards the back to keep it away from my eyes, but once pulled back it stayed in place. The liner is comfortable and kept my head nice and warm in 40 F temperature during a 60 miles ride. The liner felt a little snug with my helmet so if you have a perfect fitting helmet you might have to go a size up when wearing these liners. Overall it's a pretty good liner that provides you with good warmth. I received this product at a discounted price to evaluate and provide an unbiased review.
2948491
Fits well under a cycling helmet...fairly thin fleece.  Also if you pair this with a neck warmer or "buff", it's better and more versatile than a balaclava in my opinion.  This thing covers your ears, side and back of head well and keeps you toasty warm.  The first day I wore it on my winter bike commute, I found my hands were warmer than normal, which I think it due to this thing keeping my overall core warmer.  You will sweat a bit with aerobic activities wearing this hat, but it breathes pretty well and it doesn't feel clammy.  Great for biking in the 0 to 30 F degree range.  Above 25 or 30, its probably too much for aerobic activity.

I wish they made an XL, but the L fits my generally XL sized head pretty well.
2188340
This thing has came in handy. Really keeps my neck and head warm under my full face helmet. Isn't very thick but works well. Long enough to tuck into a shirt or jacket. Only issue is that if worn over my nose it fogs up my glasses, but I expected that.
755433
Both my husband and I wear these every time we cycle under our helmets.  Catches sweat when it is hot.  Helps keep heat in when it is cold.
1713168
I got this to keep the sweat out of my eyes while bike riding. It used to pool up in my helmet on the pads and then run down. I tried a paper towel and then after that didn't work a piece of microfiber towel, but it always moved out of position and was not the optimum fix. This headband IS the optimum fix. I just needed to adjust my helmet to a larger fit, and the headband fits great underneath. I haven't had one drop of sweat run down since. I've used it several times on days when the temp has been at or close to 100 degrees. I also have one in blue as a spare. I'll use it until winter is back, or maybe even then too since it's comfortable under my helmet.
3936751
Worked perfectly for adding extra padding to the existing padding in a helmet. Now my son's helmet fits nice and snug!  I highly recommend this product!
2102538
Works great....not as sweaty when I take off my bicycle helmet.  Can use under any hat.  Sized for a lady.  Also, great communication with seller.  They did not have color I wanted, and I was contacted and offered options right away.  Delivery time was super.
600543
I didn't notice that this was a children's hat when I placed my order and when I tried it on I was surprised that it fit me perfectly!
I ordered it to wear under my cycling helmet and because it is fitted and not a thick material it works perfectly.
I am so happy.  AND , it's lightweight so it is not hot in the summer sun.  I want one in every color.  LOL !