The M26 rocket is a series of unguided rockets fired by the M270 Multiple Launch Rocket System (MLRS). They are prepacked in canisters of 6 rounds, of which the MLRS can hold and fire two, for a total of up to 12 rockets fired at once.
M26 rockets carry cluster submunitions, initially 644 of the M77 DPICM type, and, in longer-ranged versions, 518 of the M85 DPICM. Its range is 20mi/32km in the original version and 37mi/60km in an extended-range version that carries fewer bomblets. M26 rockets, however, were replaced by the M30, which is guided and can place the smaller payload more accurately.
The major application for these area-effect weapons, informally called the "grid square removal system" when a battery of six launchers fires 72 rockets, was for counterbattery against enemy artillery, although they were also effective against troops and trucks in the open. They are not effective against armored fighting vehicles.
Both the M85, and the earlier M77 DPICM bomblets, have an unacceptable "dud" rate (i.e., failure to detonate on contact), while remaining highly explosive. The duds effectively create an antipersonnel minefield, in violation of the Ottawa Treaty and a political liability. As a result, most, if not all, future MLRS ammunition purchases will be of the XM31, which has a unitary warhead and no dud problem.