the current version is the kgsshv-carbon which uses a silicon carbide output jfet with a cascaded current source. better and simpler. you can find the schematic on your own. The GRLV is definitely NOT cheaper. extra stage at the input that subtracts out diode switching noise and a $10 voltage reference. 30 to 40 nanovolts of peak to peak output noise and voltage stability of better than .01% I don't design based on parts price.