MarShield's system of dry stacked shielding modules which interlock to form a tight, leak-free therapy room of any size or shape. Unique sine-wave shapes eliminate straight line seams and provides superior neutron, photon and particle attenuation at the joints. Available in two densities - 250 and 300 lbs./cu.ft. (4 and 5 g/cu.cm.). MarShield construction requires half the space of mass concrete vaults.