I had this tach in my 71 GS. It fit perfectly in the dash where my clock delete panel was. It fit perfectly after I modified it and it was secured to the oe bezek with tape. It is 3 5/8" in diameter. I have sive bought a repop. What you see in the pic is what I have. There is no lense or outer trim. I do have the installation instructions. $35 shipped, CONUS... <a href="http://smg.photobucket.com/albums/v226/jatidaback/71%20Buick%20GS/?action=view¤t=SDC11153.jpg" target="_blank"><img src="http://img.photobucket.com/albums/v226/jatidaback/71%20Buick%20GS/SDC11153.jpg" border="0" alt="Photobucket"></a>