IBC tanks can have a few different types of fittings. The most common is the IBC threads or Buttress threads, its a larger courser thread and come in a few sizes but your IBC tank could also have a BSP thread or a DIN thread. Follow the guide below to find the correct thread on your IBC tank.
carefully measure the outside diameter of the IBC opening.
Accurately measure the distance between the thread from peak to peak.
View the threads below to see what size you have.