Abstract: An additive device which improves the function of a computer mouse. More specifically one that appends to the form of a round, or otherwise characteristically non-axial computer mouse, such that the user is afforded the axial tactile registration (between hand, mouse, and by extension, on-screen cursor) associated with the more commonly produced elongated-type mouse. A thin shell, flexible plastic (or other) material is cast into a generally elongated form, and is at least partially hollow on the underside so as to clip snugly over and onto the body of the circular mouse. The shell is held in place by friction and/or by the use of tapes, either adhesive or hook & eye type. The button(s) of the host circular mouse remain accessible to the hand of the user, either directly or through the provision of extensions built into the additive shell.