The design, production, and performance of relatively simple, economical, and easy-to-build loop-gap resonators made of copper-clad Teflon (CuFlon) are described. Resonators were built at microwave frequencies between 1 and 9.4 GHz. A C-band continuous wave spectrum, an L-band electron spin-echo signal, and an L-band saturation-recovery signal for irradiated fused silica standard samples are presented. (C) 1996 Academic Press, Inc.