All of our Float Gauges have a 1.1/2" BSP male thread. Many Tank lids have a 2" BSP thread in the center. This adapter converts the 2" BSP thread to a 1.1/2" BSP thread allowing the float gauge to be screwed directly into the cap. This avoids the need to drill a hole in the top of the tank and secure with a back nut.
This listing is for the adapter only and does not include the actual float gauge (pictures are for illustrative purposes only)
BSP thread sizes are not the same as a simple ruler measurement. To determine the BSP size, take the imperial measurement of the external diameter of the thread and minus ¼” – this will give you the BSP size ie: external measurement is 2 ¼” then you require a 2” BSP fitting