Compatiable with the following current Kowa System S spotting scopes:
TSN-601/602
TSN-663M/664M
TSN-82SV
Compatiable with the following historical 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)