Underwater Galleries Cichlid Stone "Big Rock Box" 10 Stone Kit was created for those who want more large rocks for thier fish tanks, to either
build their rock scape taller faster, or because they have
larger fish in their aquarium!
Either way this Kit fits the bill; it has no small stones only medium  and large, all pictured on the label!
They have only one opening each; opening sizes ranging from 1 3/4 " to 2 3/4 " for larger fish. 
Wonderful for creating a complex environment of crevices and caves, they are a vast improvement over ordinary stone!
 
*Cichlid Stones are light and won't endanger the glass
*don't displace a lot of water like ordinary stone
*won't leach unwanted minerals into the water like some ordinary stone 
*create hollow cave spaces for the fish to claim as territory space