The sphero-conical vessel style of objects form a distinct group, homogeneously brought together by their shape and material. Often these objects are the same size, however very large and very small examples have been documented. The form is characterized by the "sphero-conical" shape of the body, the outline varies, but almost all have a narrow neck usually with a groove beneath the lip that would be used to tie a stopper down, and the opening is usually no more than a few millimeters in diameter. Color, texture and finish will vary, but most often these objects are dark, fine grained and compact. Firing appears to be high as to render the object impenetrable, so there is no need for waterproofing. The thickness of the walls gives the object weight and strength, and no doubt helps to improve water tightness. These objects appear throughout the Islamic world in the same form from east to west.
Over time the use of these curious vessels have sparked an impassioned debate. Many of these objects appear to have been thrown and others have a mould-formed upper section. Rumored uses of these objects include: hand grenades or incendiary bombs, to be thrown full of naphtha or petroleum with lighted brands to follow; a perfume flask; a fire-blower; a mercury bottle; a beer flask, a plumb bob , or a rose water sprinkler. One recently found at Samarra was said to have an inscription stating that it was meant to contain vintage wine.
It is clear however that these objects can serve a multitude of purposes and any of these proposals can be correct. However, one may ponder why such a very particular and laborious construction would be necessary to simply provide the required weight for a plumb bob? Whatever the case may be, Savage Smith (1997) explains: Sphero-conical vessels appear to be confined to the early and medieval Islamic periods-whatever their function, in later periods either different vessels were found appropriate, or the uses they served became extinct. - (AMD.247)