NTC thermistor for inrush suppression, type 5D-25. These devices are often used at the input of power supplies to reduce the inrush current associated with charging the main storage capacitors. 

• Resistance at 25ºc is 5Ω, lowering 0.07Ω at maximum rated current
• Maximum steady state current 8A
• Diameter approx. 25mm
• Lead spacing 10mm