Frances Lynch in A Guide to Ancient and Historic Wales: Gwynedd gives the following:
"A cairn of large boulders set on the inner edge of a low grass-grown stone bank forms a circle 6.5m in diameter. The centre is hollowed and probably artificially levelled. there has been no excavation here, so one cannot tell what or who was buried, nor whether it was built at exactly the same time as the lower circle. However, the circles' complementary setting in the landscape - one being visible from the south, the other from the north - would suggest that they were designed as a pair. The very large stone on the south side may be an earthfast boulder; the incorporation of a natural feature is quite common in monuments of this kind (see Cefn Caer Euni Circles)."