I was issued the Ops Core FAST Ballistic High Cut helmet about 4 years ago. When we first got them, they were the original version with the clip bungees instead of the hooks and the thinner forehead pad. They have since been upgraded with the new hardware and are now much more comfortable.
I have also gotten an AirFrame through work and have been playing with that for about a month. Here's my take:
The FAST helmet is the gold standard in stability. The OCC dial is hard to beat and keeps the helmet rock solid on your head when running NVG's of any type. This is all because of the fit band that goes around the head. It's also nice to have the ability to weave my headset between the shell and fit band. However, I have found that the fit band is a double edged sword. It can become uncomfortable to wear over extended periods of time because it is wrapping your head so tight. It tends to produce pressure points. The dial itself, can also cause some interference when going prone or looking up to a high angle because it wants to dig into the back of my neck. It is vertically adjustable, but if I move it higher, it digs into the bottom of my head all the time. And, while I mentioned the ability to weave the headset before as being nice, sometimes I need to wear my headset, but not my helmet. It's a pain to have to remove it every time. And, if I just wear the headset without weaving it, the fit band tends to press it into my temples. The one thing I will outright say is that I hate the Ops Core pads. They are hard and they dig into my head. But, it's an easy fix by just swapping them out with MICH pads. Overall, the FAST is a great improvement over the MICH and I like it a lot. My complaints tend to be more about the OCC dial than the helmet as a whole.https://www.tnvc.com/shop/ops-core-fast-ballistic-shell/
The AiFrame is really lightweight and comfortable to wear over extended periods. The shell design is really innovative and the passive venting actually makes a big difference in cooling the head. I like the pad system/layout too. It uses standard Team Wendy pads in conjunction with front and rear Crye-marked pads. Very comfortable. The design of the helmet also allows it wrap around the head more in the back. This provides more coverage in the back, while also conforming to the curvature of the head, making it easier to go prone while wearing armor. The chinstrap is Ops Core, so it's good to go. While it is not as stable as the OCC, it is generally stable enough for ANVIS or PVS-15 with a counterweight on the back.https://www.tnvc.com/shop/crye-precision-airframe-ballistic-helmet/
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