This is a bushing to guide cables through holes in your workbench or table. I included three kinds of revisable heads: one with a third opening, one with a quarter opening and one blind one to close the hole completely. I included the source file (RS Designspark Mechanical) to the standard STL files, if you want to change anything yourself.Just clip the top into the ring. If you printed in a larger layer width, you may have to file the tips of the clips down a little bit to prevent breaking, but this should be trivial for you. Works like a charm!Just print the ring and a matching head with enough opening to fit your cables in. Insert the ring in the 67mm hole in your table (I leave it to your imagination how to achieve this ;) ). Guide your cables through the Ring in the hole and insert the head of your choice afterwards. The separate head will keep the opening revisable at all times without changing cable connections, which was the goal of this design.