2 rounds of 12 gauge pellets, used in the Double-barreled Shotgun. They contain 8 pellets, each dealing 2000 damage. However, pellets are very inaccurate beyond short range due to the shotgun's spread. You cannot merge depleted piles, and you cannot use the 2 round magazine in the M1014 or Remington 870 (Flashlight). However, 4 stacks can be merged into a single 8Rnd. Pellets. Conversely, 8Rnd. Pellets can be converted into 4 2Rnd. Pellets by right clicking them and choosing the split option.
If given the choice between 2Rnd. Slugs or pellets, slugs are always the better choice. Pellets are ineffective past 40m, putting the player at a significant disadvantage in many engagements. However, at closer ranges, like the insides of buildings, pellets can be used to get multiple kills or headshots with a single shot.
Also note that the models used for the 2 round and 8 round piles are the same.