Left 11~18mm, right 15~25mm (you can get 27~47mm one too)
They have the both end of male and female same M42 threads
with 1.6mm thick M42 thread ring included. See the next photo.
This one > http://www.pbase.com/kkawakami/image/108670909

You can get those equivalents easily on eBay by much cheaply,
but M42 thread ring is not included though.