Rochester Gauges 8600 series spiral gauge. Tank depth should be at least 1/2” greater than the length of the gauge. The additional depth may be considered "reserve" at the bottom of the tank that will not be measured.
These gauges ship with a direct read dial. If you prefer a TwinSite Dial it can be added in 240-30 Ohms, 0-90 Ohms or 0-30 Ohms.