The only helmet that stops up to .50 cal AE and 7.62mm TKR that is used by the U.S. Government.
 
The FAST Combat Helmet from Atomic Defense is an above-the-ear (ATE) high-cut ballistics helmet that offers best-in-class protection. The rounded helmet exterior deflects or absorbs bullets away from the head, while interior padding protects the wearer from the impact force. 
We go above and beyond the competitors by subjecting Atomic helmets to extensive testing. While others may test an ATE ballistic helmet with one or two rounds, a single Atomic Defense FAST Combat Helmet is tested to withstand 18+ rounds from various calibers of weapons, including two 44 Magnum shots. Lighter rounds like copper-tip 22-caliber and 9mm hollow-point bullets barely scratch the surface. 
Features:
NIJ IIIA+ armored helmets are lighter-weight and safer than the old Kevlar tactical helmets.
Can stop the same ammunition as a level 3A+ police or military vest. (.44 Magnum, 9mm, .45 cal, .40 cal, 38, 12 gauge slug, buckshot, and many more!)
Built with the exact materials and craftsmanship we use for our police and military customers.
Tested for the latest NIJ standards.
Rapid adjusting headband.
4-point chin straps that are fully adjustable with a leather chin grip.
Fully adjustable memory padding that can be moved around, taken out, and beaten, and still retain its shape for years to come.  Feels tough at first?  Leave it on for a minute.
Tactical ARC rail system with 2-point bungee and vertical + horizontal rails.
A 360-degree all-weather coating that extends inside the helmet. 
Specs:
NIJ IIA, II, and IIIA latest 0106.01 and 0108.01 standards surpassed in testing
Aramid Shell Weight: 20-23" Size (2.3 lbs / 1.04 kg), 22-27" Size (2.6 lbs / 1.18 kg)
Total Weight w/ All Accessories: 20-23" Size (3.4 lbs / 1.5 kg), 22-27" Size (3.6 lbs/ 1.6 kg)
Fits: See chart below (Head circumference measured starting above brow-line)
Stops: 
9mm FIOCCHI, 115gr. (FMJ)
9mm WINCHESTER RANGER, 127gr. (SXT)
.357 SIG, 115gr. (JHP)
.357 SIG, 125gr. (GDHP)
.40 CAL, 95gr. (HP)
.44 Mag, 240gr. (SJHP)
7.62mm x 25mm TOKAREV NORINCO, 85gr. FMJ (STEEL JACKET)
7.62mm x 25mm TOKAREV FOREIGN, 85gr. FMJ (STEEL JACKET)
7.62mm x 25mm TOKAREV S&B, 85gr. FMJ (STEEL JACKET)
.50 CAL American Eagle, 350gr. (JHP)
5.7mm x 28MM, 27gr. (SS195)
5.7mm x 28MM, 40gr. (HORNADY BLUE TIP)
Other Compliance Standards:
VPAM: PM 1-5 with PM 6 resistance.
TR DE: SK L-2 with SK 3 resistance.
HOSDB: HG1/A-HG2 with RF1 resistance.
GOST: Class 1-2A with Class 3 resistance.
GOST 2017: BR 1-3 with BR 4 resistance.
Size
Head Circumference
Hat Standard
Inch
cm
US
S/M/L
20 - 23
50 - 59
6 1/4 - 7 1/2
L/XL/XXL
22 - 27
57 - 69
7 1/8 - 8 1/2+
Assembled and In the Box:
Upgraded IIIA+ Helmet in selected color and size
Straps and harness system (Color matched)
Exterior Velcro (Color Matched)
ARC rail system (Color matched)
Bolts holding the ARC rails in place (Black)
Bungees with self-hold integrated into the ARC rails (Color matched)
NVG Shroud (Sometimes called the NVG mount) (Color matched)
Interior Tan padding set (safety)
Interior padding sets (one thin set and one thicker set). Padding sets can be mixed and matched as long as the tan safety padding remains.
ARC to Picatinny adapter