The matrix has to be backed by a plate, both to reinforce the ceramic tiles from behind and to prevent deformation of the metal matrix by a kinetic impact. Typically the backing plate has half of the mass of the composite matrix. The assemblage is again attached to elastic layers. These absorb impacts somewhat, but their main function is to prolong the service life of the composite matrix by protecting it against vibrations. Several assemblages can be stacked, depending on the available space; this way the armour can be made of a modular nature, adaptable to the tactical situation. The thickness of a typical assemblage is today about five to six centimetres. Earlier assemblages, so-called DOP (Depth Of Penetration) -matrices, were thicker. The relative interface defeat component of the protective value of a ceramic is much larger than for steel armour. Using a number of thinner matrices again enlarges that component for the entire armour package, an effect analogous to the use of alternate layers of high hardness and softer steel, which is typical for the glacis of modern Soviet tanks.