Seiryu is the Godfather of all stones. The pinnacle of aquascaping rock. Undoubtedly one of the most popular hardscape materials available. The craggy texture and endless details in these stones allow anyone to easily create a natural-looking aquascape.  
Seiryu may slightly raise pH and water hardness. Controsoil can help balance that out. 
 
for better understanding we have attached an exampl
 
one stone of dimensions approx length 20cm, width 18cm, height 11cm has a weight of 5107gram.