Frag Grenade
This is a standard Coalition-issue fragmentation grenade. Pressing and holding the left trigger will display a visible arc which shows the grenade’s flight path. You can alter this arc by moving the right stick. These grenades can be stuck to an enemy by equipping them and pressing the Melee button while standing close to them. Must be obtained for use in multiplayer. (-StrategyWiki)
The Bolo Grenade or the Frag Grenade is the standard fragmentation grenade used by both the COG forces and the Locust Horde. The frag grenade is considered standard-issue COG equipment
The Bolo Grenade is substantially different from any other previous fragmentation grenade, both in damage and as throwing method. The grenade’s structure consists of an explosive attached to a chain-like extension that is swung around and released when enough momentum is gained to throw it. Its targeting system is also quite different, since it actually maps out a predicted trajectory (the purple line or red line if you are playing as Locust), as well as a finishing point (the distinct purple circle at the end of the trajectory marking). The grenade’s blast radius, however, is extremely small, and the grenade cannot damage foes behind a cover point no matter how close the grenade is to them. Therefore, the grenade needs to be thrown with pinpoint precision to damage, let alone kill, an enemy. The Bolo Grenade is great for flushing someone out of their cover point, however, another important use for it is that it is capable of closing Locust emergence holes. (-Gears Of War Wikia)
