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This paper presents the first demonstration of injection molding technology to enable large-scale mass manufacturing of high-performance tunable microwave filters to meet the growing needs of 5G small cell stations. This is the first time that a tunable filter satisfies all four of the following requirements simultaneously: low manufacturing cost, high quality factor, wide tuning range, and high power handling. Exhaustive research exists on the use of polymers for 3D microwave device manufacturing; nonetheless, mass-production technologies, such as injection molding, can provide low costs without compromising performance. The proposed bandpass filter implementation uses a tunable evanescent-mode cavity resonator injection molded with an acrylonitrile-butadiene-styrene thermoplastic polymer. In addition, changing the critical gap size over the resonator&#x2019;s post using a commercial microactuator provides frequency tuning. The measured filter achieves an 86&#x0025; tuning range from 2.8 &#x2013; 5.2 GHz with a state-of-the-art measured unloaded quality factor <inline-formula> <tex-math notation="LaTeX">$Q_{u}$ </tex-math></inline-formula> of 1548 &#x2013; 2573. The filter has a measured insertion loss of 0.06 - 0.1 dB with a fractional bandwidth from 7.6 - 8.4&#x0025; across the entire tuning range. Moreover, for the first time in this manufacturing technology implementation, a bandpass filter is demonstrated with power handling capabilities beyond 100 W. The manufactured device demonstrates the significant potential of this technology for the scale-up manufacturing of reconfigurable high-<inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> RF filters without compromising the performance.