spinflex designs and constructs a range of ESR probeheads for pulsed ESR spectroscopy. These probeheads can be operated in conjunction with standard Janis cryostats. The probehead operating frequency ranges are 6-18 GHz, 32-38 GH, and 92-96 GHz. They can include a variety of metallic, dielectric, or unique surface resonators as well as support wide frequency (1-100 MHz) ENDOR coils. Probeheads can also be equipped with internal cryogenic pre-amplifiers for improved spin detection capability.