Also called the "micro-focuser." This from the Starizona website. (all true)
"The Starlight Instruments SCT MicroFocuser provides the smoothest control for fine focusing. Two focus knobs allows for standard or 1/10th-speed focusing, making the MicroFocuser extremely accurate. Excellent for both imaging or visual observing, this focuser is precision-machined and anodized black with a brass fine-focus knob.
The SCT MicroFocuser is easily installed in place of the original focus knob on most Celestron 11" SCTs."
New price $189 + shipping.
I don't have the box, but it's like new.
Yours (shipping CONUS included) for $150. Paypal preferred. no fee.