Motorcycle FLUSH MOUNT Sight Glass Style External Fuel Gauge - Steel Bung - "Frenched" Style Recessed Bung - Chopper Bobber Cafe Racer Harley For those of you that would rather Flush Mount your sight glass... Can be used with gas, gasohol and oil. Brass Sight Glass - 3/4" male NPT (dry-seal) 1-1/8" Hex. Glass - Shatter resistant and Temperature resistant from -40 deg to 180 def F. Steel "Frenched" Bung - 3/4" female NPT 1.75" OD (Not including outter Flange) 1.95" overall OD (Including Flange) .70" thick flange so that you can easily blend it into the tank.