The Mvein™ restrainer is designed to facilitate mouse tail vein injections with a head cone instead of a nose cone to prevent asphyxiation. It is the first restrainer for mouse tail vein injections which enables loading of animal with head or tail first which prevents the pulling of the mouse from the tail. It is is ideal for loading mice with flank tumors in xenograft studies due to it’s rectangular design. Once mouse is loaded, the technician can rotate the restrainer 90 degrees so vein is at the top, in position for injection. Restrainer accommodates nearly all sizes of mice (15-40g).