Bourns® Multifuse® Polymer Positive Temperature Coefficient (PPTC) Resettable Fuses are overcurrent protection devices used in a wide variety of circuit protection applications. Under fault conditions a polymer PTC's resistance will rise exponentially and remain in a tripped state, providing continuous overcurrent protection until the fault is removed. Once the fault is removed, the power cycled through the PTC fuse will return to its normal low resistance state. You can access 3D STEP files of our resettable PTCs below, under Design Files.