Compatibility - Designed for Standard Oster Classic Duralast Blenders with a motor base opening of 3 3/8" (inches). - It fits models where the outside diameter of the blade base is 2 5/8". - Not compatible with Pro, Master, or Versa models. Blender Jar Base Replacement - Black Blender Jar Bottom Cap Base replaces Part # 4902. - Includes a rugged plastic gear and a gasket to help keep ingredients contained in the blender jar (glass or plastic) as they blend. Silicone O Ring Gasket - Made from durable silicone rubber with good elasticity for a reliable seal. - Soft enough to form a solid seal; useful replacement for an aging or cracked original gasket. Blender Replacement Blades - Premium Ice Crushing Blade replaces Part # 4961. - Stainless steel blade sharp enough to crush ice and thoroughly blend ingredients. - The blender motor alternates the blades forward and backward, drawing food and ice down for consistently smooth blends. Use scenarios - Replacing a worn bottom cap to restore jar stability and prevent leaks in compatible Oster Classic Duralast units. - Upgrading to the ice crushing blade to prepare frozen drinks, smoothies, or crushed ice in seconds. - Replacing a degraded gasket to restore a strong seal and prevent leaks during blending. Note - All parts are designed to match the specified Oster models and part numbers, maintaining original functionality and performance.