The Sample Type flyout lets you choose which geometry to display in the active sample slot.
This flyout has three or four buttons:
This button appears only if you have used the Material Editor Options dialog to specify a custom object for sample slots. See Creating a Custom Sample Object .
By default, the sample object in a sample slot is a sphere. You can use the Sample Type flyout to change this to a cube or a cylinder. You can also create a custom sample object by creating a 3ds Max scene that shows the object.