The Olympus CLA-11 Lens Adapter Tube is necessary when using their TCON-17 telephoto accessory lens upon the SP-590UZ digital camera (which has a proprietary female threading on it). The TCON-17 has a 55mm male thread on the rear-the CLA-11 adapts the SP-590UZ to fit the 55mm threading on the TCON-17, as well as placing the TCON-17 at the proper distance from the SP-590UZ's main lens.
Necessary when using the TCON-17 telephoto lens upon the SP-590UZ camera