This craft first appeared in PSX port of RayStorm exclusively through the 13 Ships Mode. Later it made available from player select menu in Layer Section II and RayStorm HD.
Developed as an initial prototype of R-Gray 1, R-Gray 0 lacks of Hyper Laser and Special Attack functions, and only having Manual firing mode (LS II version has both Auto and Manual modes). Unlike R-Gray 1's primary cannons, R-Gray 0's main guns fires in completely straight pattern similar to Rayforce's X-LAY. To compensate the lack of special weapons, its lock-on laser has the highest chain multiplier (x512) which makes this ship an excellent choice for scoring.
- In Raystorm HD, in-game sound effects from player shots will be replaced by those from RayForce should the player uses R-Gray 0.
- R-Gray 0's appearance varies in each version, from grey R-Gray 1 body with yellow canopy in PSX/PC port to grey R-Gray 1 body with red canopy in Layer Section II to a RVA-818 X-LAY look alike in RayStorm HD with red body (default game modes) or green body with light blue canopy in 13 Ships Mode.
- The ship is identified as "Prototype" in 13 Ships Mode