Where is the magnetic rail upgrade in Metroid 3?

In Metroid III, also known as Super Metroid, the magnetic rail upgrade, known as the "Speed Booster," can be found in the "Green Brinstar" area. Specifically, it is located in a hidden area accessible after obtaining the Super Bomb and using it to break through certain blocks. This upgrade allows Samus to gain increased speed and dash through obstacles, enhancing her movement capabilities throughout the game.