DESCRIPTION: Genuine Oster 5 cup, square top glass blender jar. Fits all Oster blender models using a 5 cup jar with a square top. Fits all Oster Kitchen Center models. This is the most common Oster jar type. All Kitchen Centers use this type of jar. This will fit all Oster blenders, but if your is a VERY old model (40 years old), using a 4 cup jar or a new model using a 6 cup jar, your lid will not fit and you may need to purchase the OS-060 lid and cap. The INTERIOR of the top of the jar measures 4" x 4".