Pretty slick deal here that someone made, you use a bolt to slide thru the idler pulley spindle and spacer, then there is a T-nut that the bolt passes thru and you tighten the whole assm. down with a nylock nut on the backside. Spacer is made from 1.700" bar stock and it uses the industry standard .625" bolt hole.
Note: This is a used item. This item might have been taken in on a trade. RBS may have inspected this item and deemed re-usable. There is no warranty expressed or implied with this item.