M26 is the basic MLRS rocket. It is unguided with a range of 20 mi (32 km). It is armed with 644 M77 DPICM (Dual-Purpose Improved Conventional Munitions) anti-personnel/anti-materiel grenades, which are dispersed over the target in mid-air and detonate on impact.
There is a newer, guided DPICM-armed MLRS rocket called the M30.
The UK Ministry of Defence has recently announced it will cease to use dumb cluster munitions and will destroy its remaining stocks of the M30. The British Army will instead procure the M31 variant which has a unitary high-explosive warhead.
References
M-26 artillery rocket Wikipedia(Text) CC BY-SA