An electronic lock box contains a secure compartment for storing keys to a structure. A projecting handle of an underlying box can be accommodated in an opening of a next overlying box, when the packages are assembled in stacked relation one upon the other, such as in palletized form. Especially contemplated rubber compositions may additionally comprise maleinized polybutadiene to synergistically improve adhesion of the rubber to a polymeric fiber coupled via contemplated adhesion promoters.