Orion part #05124: 2" extension tube used to achieve focus with certain eyepieces in certain scopes. I also have used one to insert a tight 2" laser collimator into a 2" focuser for a better fit. It is threaded for filters, and is Brand New In Box (BNIB). Price $17 including shipping in CONUS. Money order, or, if you have a 5 star rating of 10 or higher, a personal check is fine. Thanks for looking!