Model organisms with soft skulls, such as the mouse and the neonatal rat, are diffi cult to secure firmly in a traditional stereotaxic instrument. The stainless steel ear bars used for adult rats are too heavy to provide a secure hold without compressing the sides of the skull inward (which closes the airways and impedes blood flow). Further, the neonatal rat pup has no external opening of the auditory canal into which to insert the ear bars. When paired with Stoelting’s light weight, Delrin® ear bars specialized jaw holder cuffs securely clamp the zygomatic processes of the skull. The jaw holder cuffs fit over the ends of the ear bars, replacing the rubber tips, providing an alternative non-invasive means of securing the animal’s head in the stereotaxic stage.