This is a bullaun stone, a type of ancient carved rock found across early Christian Ireland, typically associated with ecclesiastical sites, in which cup-shaped depressions were ground out, possibly for use in ritual, medicine, or devotion. What makes this particular example quietly striking is its name: the 1944 to 1945 revision of the Ordnance Survey six-inch maps records it simply as "Penitential Station", a label that preserves a memory of active religious practice long after any such practice had ceased to be widely observed.

The stone measures 1.8 metres north to south and 1.53 metres east to west, and carries two almost circular basins of noticeably different depths. The eastern basin is quite shallow, only about eight centimetres deep, while the western one is considerably deeper at around eighteen centimetres. Writing in 1901, a researcher named Fahey noted that both this stone and a nearby triple bullaun, visible roughly a metre to the south-east, were regarded locally as holy wells. That identification is unusual: bullaun stones are not wells in any conventional sense, but the water that collects in their basins was evidently treated with the same reverence, and perhaps used in the same kinds of devotional circuits, as a proper spring or well would have been. The site sits within an early ecclesiastical enclosure at Roscam, a place with deep early medieval roots on the southern shore of Galway Bay.

One of the basins is currently filled with clay, which gives the stone a slightly forlorn appearance up close, but the surviving basin and the nearby triple bullaun are still legible as a pair, and the graveyard setting reinforces how continuously this small patch of ground has been used across many centuries.