The asset contains 30 rocks : 10 rocks available in 3 versions, single (original), small cluster and cluster (big).

Single rocks were made using photogrammetry then clusters were made from the singles.

Each rocks has 4 LODs which go from 1500 to ~185 tris for singles and 3000 to ~374 tris for clusters.

The most complex rock (deep dark) cluster LODs go from 5000 to ~700 tris.

Collisions use the 3rd or 4th LOD.

They use 4k² diffuse/normal and 1k² ambient occlusion.

Materials are instances of a source one.

With all of this you'll be able to fill your exterior environment with some rocks and clusters of rocks.