William Optics' model 6 and 6A flatteners have a non-standard male thread on the telescope side. This adapter # AD4-A015 allows you to couple these flatteners to a male SCT thread (2" x 24 tpi). With this, you can use the 6/6A with William Optics' Z66 and Z70 refractors, as well as with most SCT telescopes that have this thread.
Please note that this is not compatible with models other than the 6/6A (for example, 6AII and 6AIII).
Manufacturers & Suppliers of Astronomical Telescopes Since 1976