These depressions are what define it as a bullaun stone, a type of early medieval carved rock in which one or more cup-shaped hollows were ground into the surface, most likely for ritual or liturgical use, though their precise original function remains a matter of some debate among archaeologists. The larger basin, measuring 35 centimetres across and 23 centimetres deep, sits towards the eastern end of the stone; a smaller, shallower basin, just 20 centimetres in diameter and only 2 centimetres deep, sits slightly off centre. The overall boulder is modest in scale, roughly 97 centimetres long, 82 centimetres wide, and about 50 centimetres high, but its placement and markings give it a quiet significance.

What makes this stone particularly noteworthy is that it is not alone. Two further bullaun stones have been recorded within the same enclosure, making Ballinacorbeg an unusually concentrated example of this kind of early Christian site. Such ecclesiastical enclosures, typically the remains of early Irish monastic or church settlements, often preserve bullaun stones in association with other early medieval features, and the presence of three within a single boundary suggests the site held some importance in the local religious landscape. Whether the basins were used for grinding, for holding holy water, or as focuses for devotional practice, they have endured long after the community that shaped them disappeared.