This leather belt is 68" and 72" long. All treadle belts require less then 68".
To install the belt just measure the new belt against the old belt and then cut the excess off. Puncture a small hole with a nail into the end without the metal hook. Push the metal belt hook into the hole you created. Place the belt on your machine to be sure it is the correct length. Bend the metal hook to hold the ends together.