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.  
- Designed for top mount
 
- 1-1/2” MNPT tank connection
 
- Direct Read Dial
 
- Suitable for up to 25 psig maximum
 
- UL Listed for flammable liquids when gauge is 36” or less
 
- Option to add TwinSite sender Dial with 240-30 or 0-90 Ohms output
 
Contact us for additional lengths that may not be listed, our inventory is constantly changing so there’s a good chance we will have what you are looking for or we can order it.