Jay, also known by his clone trooper designation RC-1135, was a male clone originating from the genetic material of the Mandalorian bounty hunter Jango Fett. He was born on the planet Kamino, created by Kaminoan cloners to serve within the Grand Army of the Galactic Republic. Trained as a clone commando, Jay was a member of Theta Squad, and spent his entire existence with his squad mates Darman, Vin and their sergeant, Taler. During the first battle of the Clone Wars on the planet Geonosis, Theta Squad was deployed and fought alongside Delta Squad, another commando unit, against the forces of the Confederacy of Independent Systems. While engaged in combat within the subterranean caverns of the planet, Theta Squad provided covering fire as Delta Squad advanced through a compromised blast door. However, Geonosian warriors overwhelmed Jay, Vin, and Taler, resulting in their deaths, leaving Darman as the only surviving member of Theta Squad. Jay, like all clone troopers, stood at a height of 1.83 meters.
The character RC-1135 was introduced in Republic Commando: Hard Contact, a novel penned by Karen Traviss and published in 2004. Subsequent books within the Republic Commando series also made mention of him.