I am a newby at all of this. Just got my laser about a month ago. I used the original file but stretched the sides to be about 3.33 inches. I wanted to use as much of a 12 x 12 piece of wood as possible. The top and bottom are a diameter 3.85 inches. Because I stretched it I had to trim off the nobs that connect the whole thing together. I did have to rerun the top ring because it broke while I was putting it together. I ended up using a piece of 3mm walnut I had lying around for the top ring. I then used a dremel tool to cut all the nobs off. Since I am new to this, I was pretty excited I got it to work. You need to be extra careful when sliding it all together. Possibly sanding them or cutting them a little might have helped.