A rotary cone rock bit, comprises a bit body including a plurality of legs extending therefrom, each of the legs having an outer surface that includes a leading surface and a trailing surface, a roller cone rotatably supported on each of the legs, a bearing system between each cone and the leg on which it is supported, and a lubricant reservoir in fluid communication with the bearing system. A voltage reference generator may comprise a bandgap voltage reference circuit configured to output two complementary-to-absolute-temperature signals. The sample is held on a first surface of the film opened to permit access to the film. The independent corner cover is capable of adjusting the sticking position according to the size of electronic device in order to contain and protect electronic device bodies of different sizes.