For many years, body armor has had varying degrees of practicality and effectiveness in protecting persons from various types of weaponry. The body armor which best combines practicality and effectiveness is made of Kevlar, a material stronger than nylon and with tensile strength approaching steel but much lighter than steel. The performance of Kevlar body armor developed since the 1970's has been largely determined by the Law Enforcement Standards Laboratory (LESL), which is funded by the National Institute of Justice. LESL standards specify the minimum acceptable performance for each essential attribute of an item and the way the item is to be tested. The Technology Assessment Program Information Center was established to select and certify testing laboratories, coordinate the testing, and make the resulting information available to appropriate agencies. A 1978 standard for body armor has been considerably modified and updated in two revisions. The standard requires the listing of types of armor according to the bullets they will defeat and that the armor be effective when wet as well as dry. It also mandates a stated amount of resistance to 'blunt trauma,' the injury resulting from a projectile impact driving the armor into the body.