Making a Procedural Cube Mesh

I'm attempting to make a procedural mesh on a cube. I only want the sides to have the mesh, not the top or bottom.

For the vertices I'm doing the following:

 // create the vertices array
 for ( int ptsIndex = 0; ptsIndex < numVerts; ptsIndex++ ){
 // x, y, z are generated here ...
 // blah, blah, blah

     switch ( ptsIndex % 4 ){
     case 0:
         verts[ ptsIndex ] = new Vector3( x + deltaValue, y, z - deltaValue );
         break;
     case 1:
         verts[ ptsIndex ] = new Vector3( x + deltaValue, y, z + deltaValue );
         break;
     case 2:
         verts[ ptsIndex ] = new Vector3( x - deltaValue, y, z + deltaValue );
         break;
     case 3:
         verts[ ptsIndex ] = new Vector3( x - deltaValue, y, z - deltaValue );
         break;
     }
 }

Then I create my triangle array:

 mesh.triangles = new int[]{ 0, 1, 5,
                             0, 4, 5,
                             1, 2, 6,
                             1, 5, 6,
                             2, 3, 7,
                             2, 6, 7,
                             3, 0, 4,
                             3, 7, 4 };

And finally assign everything:

     mesh.vertices = verts;
     mesh.triangles = tris;
         
     mesh.RecalculateNormals();
     mesh.RecalculateBounds();
     mesh.Optimize();
 

Here is a screen shot of what I'm getting:

If any of you have any ideas on what I'm doing wrong I would love to hear it!

Thanks!

Jim