A stab vest or stab proof vest is a reinforced piece of body armor, worn under or over other items of clothing, which is designed to resist knife attacks to the chest, back and sides. Stab vests are different from bulletproof vests, most of which offer protection against firearms but afford little against stabbing with sharp-tipped objects such as knives; most stab vests afford less protection against bullets, particularly those of high caliber, but are designed to prevent serious injury by prohibiting knife penetration beyond a few millimeters. Stab vests are also needle and slash proof. Use Stab proof vests are standard issue to police officers in both the United Kingdom and New Zealand. They are also commonly worn by paramedics, security staff, traffic wardens, environmental wardens, customs officers, immigration officers, bailiffs, cash in transit officers, door supervisors/bouncers, or anyone who else may be under threat. Bulletproof vests are more commonly used by police in countries with greater firearms ownership, such as the United States and Canada; but dual-purpose armor plates that protect against both stab and firearms attacks are fairly widely available for police and also security applications. Standards "Ice pick" tests In the mid-1980s the state of California Department of Corrections issued a requirement for a body armor using a commercial ice pick as the test penetrator. The test method attempted to simulate the capacity of a human attacker to deliver impact energy with their upper body. As was later shown, this test overstated the capacity of human attackers. The test used a drop mass or sabot that carried the ice pick. Using gravitational force, the height of the drop mass above the vest was proportional to the impact energy. This test specified 109 joules (81 ft·lbf) of energy and a 7.3 kg (16 lb) drop mass with a drop height of 153 cm (60 in) and an ice pick with a 4 mm (0.16 in) diameter with a sharp tip with a 5.4 m/s (17 ft/s) terminal velocity in the test. The California standard did not include knife or cutting edge weapons in the test protocol. In this early phase only titanium and steel plate offerings were successful in addressing this requirement. These textile materials do not have equal performance with cutting-edge threats and these certifications were only with ice picks and were not tested with knives. United Kingdom The Police Scientific Development Branch (PSDB) work studied