Post Serial no, and deck size to make sure you got the right belt. If you are just measuring it, it would be a B87. Best way to do this is to loosen the guides at the engine pulley and take the triangle plate with the two idler pulleys on the deck off. Take the link off that goes to the engage lever and slide the triangle plate up off the pivot post. Take an impact wrench and take the v idler off and wrap the belt around it and slide it back down on the bolt and tighten nut. Sometime you have to take the flat idler loose as well to get the belt clear the idler. Slide the triangle plate back down over the pivot post making sure the belt goes out side the v idler and inside the flat idler and around the engine pulley and inside the pivot post. Put belt around the deck pulley on last since it is easier to get on this way. Put the engage link back on and engage the belt put the belt guides back like they were at the engine pulley. Tighten the nut on the engage link so the spring is compressed to 1 7/8 inches.