Most darkroom processes don't need to be precisely accurate. Just consistent. I have two Gralab 300's in my darkroom for general process timing, and a Gralab 450 to control exposures on my enlarger. I've also got a Gralab 900 that I don't use. It has to be one of the weirdest and most difficult to use timers ever made. If anyone wants the 900, contact me, I'll sell it cheap. It works fine for a Rube Goldberg, but it's in cosmetically rough condition.