Battlefield 4 as a sidearm optic called the Delta (RDS).
— Battlelog Description
The Delta (RDS) is a sidearm exclusive red dot sight available in Battlefield 4. It is the third and final optic unlocked for sidearms, after the Mini red dot sight and the Ghost Ring Sight, requiring 80 kills to unlock.
The Delta is unique among the other red dot sights in the game as it uses a red triangle as a reticle, as opposed to the single dot used by the Mini, Reflex, and Coyote. Compared to the Mini, the Delta sports a much slimmer frame, allowing the player to retain visual awareness around the target, and the red triangle is much more noticeable in chaotic environments compared to the Mini's small red dot.
The Delta (RDS) is a sidearm exclusive attachment featured in Battlefield Hardline.