Throat is defined as the part of the extruder that connects the heatsink to the hot end. As is immediately obvious, there are different types of throats according to the drawing of the printer and especially according to the processed filament, whether 1.75 mm or 3 mm.
A detail to note when you want to proceed with the purchase that has a big difference is the interior of this component. Throat exist with a small tube of Teflon inside, which improves the smoothness but has temperature limits. With this version it starts to become dangerous to push above 250/255 degrees.
Other version, the all-metal, can withstand much higher temperatures, is the right choice to use for printing with special materials that must be extruded from 250-300 degrees.
A small note: in the vast majority of cases this component has a metallic appearance, but it is not purely metal, so it can be ruined / broken if treated as if it were metal.
The throat can be found through all major e-commerce, you have to pay attention to the measures.
Look all throat out there and identify your here!