Each half preserves part of a single carved basin, so that the full hollow only becomes apparent when you understand what you are looking at across two separate fragments. This is a bullaun stone, a type of early medieval stone featuring one or more cup-shaped depressions, often associated with early Christian sites in Ireland and traditionally linked with ritual or devotional use. The curiosity here is that the break is total: neither half makes complete sense without the other.

By 1950, the antiquarian Harold Leask had catalogued the two pieces separately, listing them as numbers 40 and 41 in his guide to Glendalough. At that point they were outside St Kevin's Church, the small early medieval oratory that stands within the monastic enclosure. When Healy recorded them in 1972, they were still outdoors, and the measurements taken then give a precise sense of how little survives of each piece. The first half measured roughly 0.43 metres by 0.27 metres, with a basin diameter of 0.15 metres and a depth of 0.14 metres; the second half was slightly larger, at 0.5 metres by 0.35 metres, with a basin of 0.16 metres across and 0.11 metres deep. Since then, both fragments have been moved inside St Kevin's Church, presumably for their protection.