fragmentation grenades, the explosive filler is usually of a greater weight and volume, and the case is much thinner – the US MK3A2 concussion grenade, for example, has a body of fiber (similar to the packing container for the fragmentation grenade). These grenades are usually classed as offensive weapons because the small effective casualty radius is much less than the distance it can be thrown. The concussion effect, rather than any expelled fragments, is the effective killer. In the case of the US Mk3A2, the casualty radius is published as in open areas, but fragments and bits of fuze may be projected as far as from the detonation point. They have also been used as depth charges (underwater explosives) around boats and underwater targets; some like the US Mk 40 concussion grenade are designed for use against enemy divers and frogmen. Underwater explosions kill or otherwise incapacitate the target by creating a lethal shock wave underwater. The US Army Armament Research, Development and Engineering Center (ARDEC) announced in 2016 that they were developing a grenade which could operate in either fragmentation or blast mode (selected at any time before throwing), the electronically fuzed Enhanced Tactical Multi-Purpose (ET-MP) hand grenade. Some blast grenades with cylindrical bodies can be converted into fragmentation grenades by coupling with a separate factory-made payload of fragments wrapped around the outside: a "fragmentation sleeve (jacket)", as shown in the WW2 "Splittering" sleeves for the stick grenade and M39 "egg hand grenade". Anti-tank A range of hand-thrown grenades have been designed for use against heavy armored vehicles. An early and unreliable example was the British Sticky bomb of 1940, which was too short-ranged to use effectively. Designs such as the German Panzerwurfmine (L) and the Soviet RPG-43, RPG-40, RPG-6 and RKG-3 series of grenades used a High Explosive Anti-Tank (HEAT) shaped charge warhead using a cone-shaped cavity on one end and some method to stabilize flight and increase the probability of right angle impact for the shaped charge's metal stream to effectively penetrate the tank armor. Due to improvements in modern tank armor, anti-tank hand grenades have become almost obsolete. However, they were used with limited success against lightly-armored Mine-Resistant Ambush Protected (MRAP) vehicles designed for protection only against improvised explosive devices in the Iraqi insurgency in the early 2000s. Non-explosive grenades Less-than-lethal Stun (flashbang) A stun grenade, also known as a flash grenade or flashbang, is a non-lethal weapon. The first devices like this were created in the 1960s at the order of the British Special Air Service as an incapacitant. It is designed to produce a blinding flash of light and loud noise without causing permanent injury. The flash produced momentarily activates all light sensitive cells in the eye, making vision impossible for approximately five seconds, until the eye restores itself to its normal, unstimulated state. The loud blast causes temporary loss of hearing, and also disturbs the fluid in the ear, causing loss of balance. These grenades are designed to temporarily neutralize the combat effectiveness of enemies by disorienting their senses. When detonated, the fuze/grenade body assembly remains intact. The body is a tube with holes along the sides that emit the light and sound of the explosion. The explosion does not cause shrapnel injury, but can still burn. The concussive blast of the detonation can injure and the heat created can ignite flammable materials such as fuel. The fires that occurred during the Iranian Embassy Siege in London were caused by stun grenades. The filler consists of about of a pyrotechnic metal-oxidant mix of magnesium or aluminium and an oxidizer such as ammonium perchlorate