For police officers, the most common choice is the type that can stop the caliber of weapon carried by the department's officers. Each individual has to evaluate their home town area or assigned area where they will work, and the possible threat levels that they might encounter in that area. When your life is on the line, it would make sense to find the most protective vest possible that offers the most flexibility so that you would not mind wearing this protective vest day after day for extended periods of time. Here is a bit more information about each level of ballistic protection.
I: A level I vest is the lightest on the market, but has the least amount of stopping power. They are capable of resisting.22 caliber rifle bullets (lead) with an impact velocity of 1,050 feet per second (or less). They can also stop 38 Special rounds, as well as.32 and.25 caliber handgun rounds.