This article demonstrates the application of microstrip-to-microstrip transitions to realize wide-band bandpass filters (BPFs) for a variety of 5G/6G applications. The basic design approach employs two back-to-back connected microstrip-to-slot-line transitions in a two-layer implementation with a middle ground plane layer. Innovations on the basic design that apply slot lines and stubs on the various layers to affect Q, passband flatness, group delay flatness and phase response are developed for a variety of filter applications. Applications highlighted include ultrawideband transitions, wideband transition-based BPFs, Diplexers, dual-band filters, reflectionless filters and flat group delay filters.