The base on our current blender is spring loaded and requires a slightly different action to secure it to the Chef. These blenders will fit all Chef and Major models manufactured after 1976, including the A901, but not the A701 or A707. In order to fit the blender, please carry out the following: - With the handle facing away from you and pushing slightly in a downward direction, turn the handle until you feel the biting point. - Push the blender fully down on to the Chef/ Major. - Turn the handle clockwise as far as it will go to fully secure the blender. Your blender is now ready for use.