FTR10D621K is an electronic part manufactured by FTR, featuring varistors 505V 1025V 2.5KA through hole, with a P=7.5mm RoHS rating. It is a two-terminal non-linear resistor that can act as a transient voltage suppressor. This part is designed to provide protection against large voltage spikes that may occur on AC powered electrical circuits. It can absorb large amounts of energy and it is noted for its high surge absorption capability. The FTR10D621K is typically used to defend sensitive electronic components from sudden, potentially damaging, voltage spikes.