Captive 1/4 x 20 screw with black knob. Curve on base to fit C8 and presumably a Meade 8" SCT. I used it to piggyback a C90 on a C8, so it is very sturdy! $20.00 + $4.00 shipping CONUS. Money order, bank check, or PayPal + 3% (.75). Thank you for looking!