I had already a T2. I wanted a second for use with a second telescope for astrophotography. This T2 ring perfectly fulfills its function of ACCOUPLAGE between the Canon EOS 550D and T-adapter SC screwed onto the telescope Celestron or Meade (Canon settings are accessible only in the manual position). I bought this adapter ring on Amazon for its lower price than competitors specialized in astronomy. I am fully satisfied with this transaction.