The stone, roughly 45 centimetres by 28 centimetres, has a single hemispherical hollow worn or carved into its upper surface. This is a bullaun, a type of stone featuring one or more cup-shaped depressions that appears repeatedly at early ecclesiastical sites across Ireland. Their exact purpose remains debated, but they are associated with early Christian and possibly pre-Christian ritual practice, and the hollows were often used to collect rainwater believed to have curative or protective properties.

What makes this particular bullaun quietly curious is its recent history as much as its ancient one. It was not found in situ at the oratory but was recovered in the 1930s from a ploughed field nearby, having presumably been displaced at some point before that. It was subsequently placed outside the oratory doorway, the ruined building it most likely once accompanied. That oratory survives in poor condition, though it retains a decorated lintel, and there were formerly traces of other structures at the site. The whole complex does not appear on Ordnance Survey maps, which means it has slipped past the usual routes of casual discovery.