Amazon.com: FYSETC HT-NTC100K Thermistor Cartridge 3D Printer Ender 3 V2 Hotend Parts 3950 XH2.54 2Pin Compatible with Ender 3/Ender 5 Pro CR6 CR10 A8 Maker Pro Extruder Hotend-Pack of 3 : Industrial
The thermistor is a temperature sensor that varies the resistance.
Ntc 100k Ohm B3950 Thermistor 3x15mm Cartridge Sensor High Temperature For 3d V6 Upgraded Heater Block 3d Printer - 3d Printer Parts & Accessories - AliExpress
Sensor de temperatura con Arduino y Termistor - Las cosas de Dani