Gravel, Crushed Aggregate, Sand..
Every project is different, and there are different types of material that can be used inside RutGuard®. The typical rule of thumb when it comes to sizing, is to make sure that the size of the rock does not exceed 3/4 inches of the size of the cell opening. This is because if you fill the cells of the RutGuard® with material that is too large, it weakens the overall purpose of why you installed the geocell in the first place: to confine and strengthen your material.
Think of it this way:
If you fill a jar with golf balls, you will see several empty spaces in between the golf balls. But, if you fill that same golf ball filled jar with some sand or crushed gravel, the smaller material will fill in the holes around the golf balls. This is similar to what is happening in the cell. You want a mixture of medium and small material to fill in as much as space as you can within the cell.