The Edstrom Vari-flo valve is precision machined from solid brass. The small diameter of the stainless steel stem that the animal must move to release the water and the low force required to move it makes this valve great for small creatures, such as mice, guinea pigs and finches. The rate that the water is discharged from the Vari-flo valve can be adjusted over a wide range to best suit your animals and reduce spillage of water into the cage as the animal drinks. Rate of adjustment can range from 20cc per minute to 100cc per minute.