Measure the diameter of your tube to determine the correct size.
If we do not have the size that you need, please contact Joe Nastasi at Parallax Instruments. Joe is also a great source for a variety of mounting rings for other scopes. Let him know which mounting plate you plan to use and he will drill the hole pattern you need. If you are planning to use them with our mounting plates, specify the Astro-Physics hole pattern on the top and bottom of the rings. Please order the rings directly from Parallax Instruments.