Abstract: Filters include a housing having a top wall, a bottom wall and one or more side walls that define an internal cavity; a plurality of resonators that are mounted within the internal cavity with a first space provided between a pair of adjacent resonators; and a coupling-tuning element mounted on one of the walls of the housing. The coupling-tuning element comprises one or more solid dielectric materials and is capable of extending into the first space to tune the coupling characteristics between the pair of adjacent resonators.