Designed to require no oil bath, the compact SRL Series of high-accuracy resistance standards measure just 3.4"H x 4.2"W x 5.0"D and weigh only 1.5 lb. The units are said to exhibit virtually zero temperature coefficient near 23°C and typically less than 1-ppm change between 18°C and 28°C. The SRL standards are available in a range of values, from 1 ohm to 19 Megaohms. Custom and special values suitable for RTD such as 25 ohms are also available. Tests have shown this series to be highly stable, typically varying less than 1 ppm per year, yet the series is claimed to be more economical and cost-effective than other standard resistor choices.