http://www.bulletproofme.com/Ballistic_Protection_Levels.shtml
The cut and paste does not work well for this, but here it is:
Level I
.38 Special at 850 fps (feet per second)
(259 mps - meters per second
.22 at 1,050 fps
(320 mps) NOT RECOMMENDED
Early generation ballistic fibers, though bulkier, only stop fragmentation and low velocity pistol ammunition.
Sometimes PASGT army surplus flak jackets are passed off as “about Level II-A”, but in our tests 9 mm penetrated. Excellent riot gear or paintball equipment, but not recommended for pistol ballistic protection.
II-A
~16 layers of Kevlar® 129
9 mm FMJ (Full Metal Jacket) at ~1,090 fps
(332 mps)
.357 Magnum JSP (Jacketed Soft Point) at ~1,250 fps
(~381 mps). Minimum Recommended...
...for the vast majority of threats encountered on the street, though you would sustain more blunt trauma injury than Level II or III-A. The thinnest and best for concealability and comfort.
II
~ 22 layers Kevlar® 129
9 mm FMJ, at ~1,175 fps
(~358 mps)
.357 JSP at ~ 1,395 fps
(~425 mps). A great balance...
...between blunt trauma protection, versus cost, and thickness / comfort / concealability. Handles the blunt trauma of higher velocity +P rounds better.
What we recommend most often for concealable wear.
III-A
~30+ layers Kevlar® 129
9 mm FMJ at ~1,400 fps
(~427 mps)
.44 Magnum at ~1,400 fps
(~427 mps). 1,400 fps is to cover the velocity of 9 mm FMJ from a submachine gun.
The highest blunt trauma protection rating in soft body armor. The best for very high-risk situations to cover more of the uncommon or unusual threats.
Minimizes blunt trauma injury to allow more effective return fire.