This is the "BLS" 3.5x teleextender for the Taurus Tracker III, made to use with a Schmidt Cassigrain. They sell new for $100 from Taurus Technologies. I'm asking $75. I'm also looking for the "ATF" piece for the Tracker III (The "Long Telescope Port Adapter", which will hold their reducing lens.) I'd be willing to trade for it, which retails for $70.