a bulk material container comprises a shell made from suitable material , such as aluminum or stainless steel . disposed within the shell is a follower . the vertical position of the follower varies with the level of flowable bulk material stored in the shell . a permanent magnet is carried by the follower for movement therewith and a magnetic switch operatively responsive to the magnetic field created by the permanent magnet is attached to the exterior of the shell to detect the height of the permanent magnet . a level indicator is responsive to the operation of the magnetic switch for indicating the level of the follower .