The Covenant needler fires self-guiding shards of an unknown material that will penetrate any soft object no matter the angle of impact.  They then imbed and after a short time explode, with the intensity of the explosion amplified by an increase in shards.  Each individual shard explodes with an energy of 20 to 45 kilojoules.  It takes only 7 to drain the shields of a Spartan's battle armor.