The stone, measuring 1.62 metres long and just 10 centimetres thick, serves as the cover stone of the burial beneath it, meaning its carved surface has spent centuries pressed against the weather rather than sheltered inside a church or museum.

The decoration carved into its surface is careful and considered. A central double band runs the full length of the slab in low relief, connecting to a roundel at the centre and three D-shaped terminals at the western end, the uppermost of which carries fret ornament, a geometric interlaced pattern common in early Christian stonework, along with a small raised boss at its angle. Below the roundel, another pair of D-shaped terminals appears, and towards the lower end of the slab faint traces of carving mirror the arrangement at the top, suggesting a symmetry that time and exposure have largely worn away. An incised border, a shallow line cut along the edge, survives in places. What makes this slab particularly notable is its material: limestone is unusual on High Island, where the geology runs to harder stone, and this is one of only two limestone slabs recorded there, the other being the footstone of the same grave.

High Island, known in Irish as Ard Oileán, lies off the coast of Connemara and is accessible only by boat in suitable conditions. The graveyard is part of an early Christian monastic site, and the carved slabs associated with Grave 3, of which this is one, represent some of the more elaborate surviving decoration on the island. The stone was recorded in detail by Fisher in 2014, building on earlier work by White Marshall and Rourke, and sits alongside two other decorated slabs connected to the same burial.