What distortion did cliff Burton use?

Cliff Burton used several distortion pedals throughout his career, but his most famous distortion sound came from the Boss HM-2 Heavy Metal pedal. He used this pedal in conjunction with a Marshall JCM800 amplifier to achieve a thick, saturated distortion tone that was perfect for Metallica's heavy metal sound. He would also sometimes use a Rat distortion pedal to add extra aggression to his sound.