Moss Motors has developed a new style tensioner assembly for the JR M45 supercharged Miatas and it is now standard in all systems! Redesigned Heavy-Duty Black Anodized Billet Tensioner Bracket Redesigned Idler Pulleys are crowned. The crowned design causes the drive belt to track in the center of the pulley all the time, instead of riding on one edge or the other. The redesigned tensioner system virtually eliminates belt slipping, an important feature, especially on higher boost systems. The kit includes 2 new idler pulleys as well. You will need to order a belt separately for use with the redesigned tensioner based on your application. Please note that this kit cannot be installed on cars without power steering.