Aside from your actual rig your helmet is arguably your most important piece of gear.
Seeing as there are no companies (yet) specifically making helmets for BASE we have to look outside our sport to find suitable ones. Most common are other extreme sports - Skateboarding, Skiing & Snowboarding, and BMX to name a few.
There are a lot of choices out there and a lot of questions to ask yourself when trying to decide on what to get. A lot of people fall into the trap of buying a certain brand/style just because thats what their friends have but it's always good to do a little research yourself (we recommend the same for everything BASE related) before making a decision.
Some seemingly obvious questions to ask yourself are:
-What kind of climate will you be jumping in?
-How long are you going to be wearing your helmet for at a time?
-Will you be doing primarily jumps that are Slider Up, Slider Down, or a mixture of both?
-Full Face or Open Face?
While all the above are important, the no.1 thing to ask yourself is: Will this helmet protect my head against an impact?
For those of you who like to nerd out a little more read on for the 5 things we recommend you take into consideration before purchasing a helmet for BASE.
1- Impact Rating
Every manufacturer that BASEgear.net carries makes a certified, quality, single impact helmet. This means that if you take a hard enough hit that dents, cracks, or damages the helmet that it has done its job by absorbing the impact. If any of these things happen we recommend you no longer use the helmet. The manufacturer's also recommend that you replace your helmet after roughly 5 years as the protective material can break down over time decreasing it's functionality.
If you want an impact rated helmet you are pretty much writing off all skydiving helmets. These are not made to absorb impact. Skydiving helmets are basically $400 GoPro mounts.
Within the past couple years or so Cookie's G3 helmet has become very popular for Wingsuitting and Tracking jumps which is the one exception to the rule 'don't base jump with a skydiving helmet' as you are usually (dangerous word) so far away from the object on deployment that the chances of an object strike is extremely low.
How can I tell if a helmet is rated for impact?
All helmets sold on this site are impact rated but if you choose to purchase a helmet elsewhere the symbols below are what you must look for.
CE: The European standard which all helmets must meet or exceed in order to be sold in the European marketplace.
ASTM: The safety standard which all helmets must meet or exceed to be sold in the United States marketplace. All helmets found in the United States will meet the ASTM standards. Some helmets will also be marked CE, meaning they meet the standards of both the ASTM and CE.
2- Make sure it fits.
Making sure that your helmet fits correctly is going to be key to ensuring it can do it's job when necessary.
How to make sure your helmet is the correct size
Put the helmet on your head with the forehead first, then seat the rest of the helmet to the back.If the helmet fits correctly there should be no gaps anywhere and all of the padding from the helmet should fit flush against your head.
When you have the helmet on, give it a few soft pushes from front to back. It should remain snug so that when you push on it, the skin on your forehead and eyebrows move with it. Also, gently twist the helmet from side to side causing your head to move with it. If the helmet flops around, or moves without your head, the helmet is too large. If the helmet does not sit flush down on your head it is too small. Having one or the other will result in not having adequate protection.
3- Style
There are a few different styles of helmets. Each one having it's own, specific purpose.
Half Shell helmets can sometimes have soft ear pads on an otherwise hard shell helmet. The soft ear pads are typically removable and the liners are usually removable and washable. These helmets are the most popular style of helmet for jumpers as they are not too warm and not too cold. They serve really well as a good general purpose helmet for BASE. 
Full Shell helmets have full coverage that includes hard sides over the ears. These are popular with jumpers who really like a snug fit all over your head and who spend a lot of time in the mountains or in colder climates.
Full Face helmets have a chin guard and a visor. These offer the most protection and we strongly recommend them when jumping Solid Slider Down Objects for the most protection. They are often the pretty heavy sometimes weighing almost double the other styles above.
4- Ventilation System
If you are going to be wearing your helmet while hiking or climbing you're going to want to have some way for air to travel through without overheating or fogging up your goggles/sunglasses. A lot of helmets will have venting directly on the brow or forehead area of the helmet which will provent the fogging.
Adjustable Vents: Some helmets will have some switch or toggle located on the helmet that allows you to open and close the vents to regulate your temperature. You'll see these a lot on bike helmets. We do not currently sell any helmets with adjustable vents but they are worth mentioning and another option to consider.
Fixed vents: Located on the helmet and are always open to allow airflow to continuously pass through the helmet. These can be little vents at the front and back or big holes on top.
5- Color and Looks
Having a helmet that you like the look and color of is obviously important BUT as you can see it's the last thing on our list. Don't go out and buy a helmet just cause it looks cool or because it matches your rig. By all means look for one you like, just ensure that you have taken all the above criteria into consideration.
We hope this little guide was helpful for all you GearNerds out there. Stay Safe.