A bracket construction for fixedly securing a cylindrical tank such as the oxygen tank of an emergency vehicle in a vertically upright position wherein the tank is easily releasable which accommodates various sizes and configurations of upper neck sections having a backing plate with a lower surrounding member for receiving and retaining the tank bottom therewithin and an upper surrounding member including aU-shaped channel for receiving the tank neck therewithin. Two uniquely shaped bracket cams are pivotally mounted relative to the upper surrounding member and resiliently biased with respect thereto such that they can be manually manipulated or directly contacted by the arcuate neck of a tank to move to the opened position to allow exiting or entry of the tank. A lower auxiliary floor surface is pivotally secured relative to the lower surrounding member for varying the vertical dimension for accommodating tanks of various lengths and shapes.