Rochester Gauges 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
 
- TwinSite Sender Dial 240-30 Ohms (0-90 Ohms and 0-30 Ohms also available, please call or email to place order)
 
- Suitable for up to 25 psig maximum