This mobile suit is a prototype MS developed under the "F Project," a smallscale MS development initiative by the Strategic Naval Research Institute (S.N.R.I.). The F91 was designed with the goal of achieving "maximum performance in an MS." The development was based on the F90V, equipped with a highoutput generator. In terms of weaponry, it features a VSBR (Variable Speed Beam Rifle) and a beam shield. Additionally, the F91 is equipped with a biocomputer system to assist with operation, significantly enhancing the suit's tracking capabilities.