Dynamic nuclear polarization (DNP) enhanced nuclear magnetic resonance (NMR) spectroscopy has emerged as a new and growing application for high-frequency, continuous wave (cw) vacuum electronic devices capable of producing powers in the range of tens to hundreds of watts at millimeter-wave and terahertz frequencies. As an original equipment manufacturer of gyrotrons for Bruker Biospin DNP spectrometers, CPI has developed continuous wave (cw) gyrotrons at 263 GHz, 395 GHz, and 527 GHz. Design and performance details for the second-harmonic 395 and 527 GHz gyrotrons will be presented.