Precise, low insertion loss, and compact integrated delay lines are the key components in realizing wideband mm-wave and sub-THz beamformers. This article presents recent progress on low loss, compact, integrated tunable delay line design for beamformer applications. A number of tunable delay line approaches are discussed including a tunable transmission line with switchable capacitance and inductance, continuously tunable capacitance and inductance delay lines, and "trombone-inspired" switchable propagation distance passive N-cell delay lines. Each approach is compared to highlight advantages and limitations.