Thermal Detonators are a highly destructive type of grenade found in the Star Wars universe.
Thermal detonators are issued to all stormtroopers and have no markings and individual codes, meaning that even if someone took a dead stormtrooper's thermal detonator, they would not know the activation code for it.
Thermal detonators are either round, cylindrical, or club like. (citation needed)
Thermal Detonator Strength
The SWEGWT states that thermal detonators use "fusion reaction" of a substance 'Baradium', and that thermal detonators shells are also designed to fragment. Thermal detonators, while being grenades, are also strong enough to be used as demolotion charges with enough force to blast a hole through 2 meters of permacrete (citation needed)
The SWEGWT states that the standard Imperial thermal detonator has a blast radius of 5 meters, with larger grenades having lethality ranges of 20 and even 100 meters. However, it is probably that these larger grenades are launched by either mortars or other artillery since the blast radius would kill anyone in the immediate area, including the person who threw the detonator in the first place.
Star Wars: Return of the Jedi: Leia, under the disguse of a bounty hunter, brandishes a thermal detonator, causing everyone in Jabba's throne room to cringe back in fear.
Star Wars: Knights of the Old Republic: When the player reaches the hangar that the Ebon Hawk is stored in, after defeating Davik Kang and Calo Nord, Calo Nord reveals a thermal detonator, saying "this thermal detonator will blast us all to bits" before being crushed by falling debris. It should be noted, that the hangar room this occurs in is very wide, and the player is easily standing some 20 feet away from him.