 "55" features collaborations with Fetty Wap, Cam'ron, Wyclef Jean, Carly Rae Jepsen, Matthew Koma, Magic Man, Alex Newell, POWERS, Phoebe Ryan, Justin Tranter, Walk the Moon, and X Ambassadors.Work for the album began to show in August 2015, when the single "Classic", released for their "So Classic" EP, was re-mastered and released as a 2015 re-release, adding new feature vocals from Fetty Wap along with POWERS.Afterwards, the duo went on to uploading a brand new music video for their collaboration with Alex Newell, titled "Collect My Love" and was classed as the second re-release from their "So Classic" EP.