Coflein has the dimensions of this substantial round cairn as:
“22m [c72ft] diameter and 1.6m [c5ft] high” (J.Wiles 01.09.04). It was excavated during 1907 (RCAHM 1917 (Carmarthenshire), 173 [519]), “when a second mound, was said to have been removed”. (source Os495card; SN53NW1)
At the time of posting note that the official roadside parking indicated upon the map is conspicuous by its absence... although technically possible upon the rough verge. Fortunately, I had opted to walk across Mynydd Llanllwni from the excellent Crugiau Giar cairns (c3.5 mile ‘round trip). There is the massive, albeit very denuded, circular footprint of another cairn to the north across the road.