What type of ESR sample tube to purchase?

We recently had a grad student ask us what type of ESR sample tube to purchase. He was performing a quantitative experiment involving a metal complex dissolved in toluene. The point of the experiment was to study the interaction of various wavelengths of UV radiation upon the interaction of the metal complex. We recommended that precision Suprasil ESR tubes be used, primarily because the solvent height will remain the same between samples, which will keep the sensitivity of the cavity about the same. Also, the synthetic quartz can transmit wavelengths down to 190nm, which is what the experimenter required. Our recommendation was to use Norell Part No. S-4-EPRSQ-250P, a 4mm OD X 250 mm length precision ESR tube which is the typical size used in 4 or 5mm finger dewars.