4 Walls is the fourth studio album by South Korea-based girl group f(x), released by SM Entertainment and Genie Music on October 27, 2015. A dominant electropop and synthpop record that incorporates various genres, such as house, EDM and UK garage, 4 Walls was composed by several production teams and songwriters, namely LDN Noise, The Stereotypes, Kenzie, Ryan S. Jhun, Makeba Riddick, Carly Rae Jepsen, among others, with Lee Soo-man served as the executive producer of the release. It marked f(x)'s first major release since Red Light in July 2014, and subsequently the group's first and currently the only major release as a quartet since the departure of former member Sulli in August 2015.

Dimension 4 – Docking Station was the debut concert tour of South Korean girl group f(x) launched in support of their fourth studio album, 4 Walls. It consisted of three shows in Seoul, South Korea, and eight shows throughout Japan. The tour commenced at the Olympic Hall in Seoul, and concluded at the Yokohama Arena in Yokohama, Japan. A concert DVD, f(x) Dimension 4 – Docking Station in Japan, was released on July 6, 2016, in Japan.