Description from Coflein:
“Located on a broad terrace on the NW-facing scarp of Mynydd Llangynidr.
The row comprises five upright stones, closely spaced, and is 5m long, aligned NE-SW. The tallest is about 1m high, the shortest 0.5m. At the SW end of the row is what appears to be a fallen monolith. It measures 2.9m long (NW-SE), 0.8m wide tapering to a point at its SE end, and 0.6m thick.
Some 44m to the NE of the row, and roughly on the same bearing, is an outlier set loosely in the peat.”
Apologies for poor translation, but the name appears to mean something like “large white stone in the heather” (carreg = stone; wen = white; fawr = large; Y R(h)ugos = clumps of heather). I’m sure someone can do better!