The grounding screw are suitable for most following land: 

1) Topsoil: Sand, gravel, silt. 

2) Flowing sand: Liquid and muddy ground water. 

3) Friable soil: Loose sand, Gravel or mixed. 

4) Middle heavy friable soil: Sand, gravel, silt and clay. 

5) Difficult soils: More than 30% are stone which diameter bigger than 63mm. 

6) Moveable chisley soil: With rock, fay, crispness, slate, rotten soil. 

7) Moveable stereoplasm rock: Little rock with high structural strength jointed and weather-defined 

8) picture