High-quality zoom eyepiece with rotating eyecupCompatible with the following current Kowa System S spotting scopes:TSN-601/602 | TSN-663M / 664M | TSN-82SVCompatible with the following no longer available spotting scopes:TSN-603/604 | TSN-661/662/663/664 | TSN-1/2/3/4 | TS-601/602 | TS-611/612/613/614 | TSN-820 / 820M (requires TSN-EC1A adapter ring)